Transformation of phenolic acids during radical neutralization.

Negative influence of reactive oxygen species on living organisms and stability of food products is the reason for significant interest in the substances exhibiting antioxidant properties. Phenolic acids are very popular among the known diet antioxidants. The paper presents the results of research on the application of chromatographic measurements for determination of antioxidant changes and products of radical neutralization reaction for the chosen phenolic acids (caffeic, ferulic, p-coumaric, protocatechuic and vanilic). The measurements were performed using the ABTS method in a long period time (8 days). The experiments have shown that the examined acids were depletion to ca 50 h but the reaction products (dimers or quinones) were converted into new compounds, observed in both methanolic and ethanolic measuring systems after a given period of time. The obtained results seem to be important in the context of living organisms because the biological activity of transformation products and their impact on human health have not been fully recognized yet. Moreover, the presented results can be interesting for both the producer and the consumer of food as generated substances may have influence on the nutritional value as well as the taste and aroma of the food in which phenolic compounds are applied. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-023-05879-w.

Cannabigerol (CBG) signal enhancement in its analysis by gas chromatography coupled with tandem mass spectrometry.

PURPOSE: According to recent reports, cannabigerol (CBG) concentration level in blood and body fluids may have forensic utility as a highly specific albeit insensitive biomarker of recent cannabis smoking. While the analytical sensitivity of cannabidiol (CBD), Δ9-tetrahydrocannabinol (Δ9-THC), cannabichromene (CBC) or cannabinol (CBN) estimation by gas chromatography-mass spectrometry (GC-MS) is similar and sufficiently high, it is exceptionally low in the case of CBG (ca. 25 times lower than for the other mentioned cannabinoids). The purpose of this study is to explain the reasons for the extremely low analytical sensitivity of GC-MS in estimating CBG and to present possible ways of its improvement. METHODS: Nuclear magnetic resonance (NMR) data and GC-MS responses to CBG and its various derivatization and transformation products were studied. RESULTS: The validation data of individual derivatives of CBG and its transformation products were established. CBG silylation/acylation or hydration allows to decrease LOD about 3 times, whereas the formation of pyranic CBG derivative leads to 10-times decrease of LOD. The paper enriches the literature of the subject by providing MS and NMR spectra, not published so far, for derivatives of CBG and its transformation products. The most likely cause of low GC-MS response to CBG is also presented. CONCLUSIONS: The presented results shows that although the signal increase of CBG can be obtained through its derivatization by silylation and/or acylation, the greatest increase is observed in the case of its cyclization to the pyranic CBG form during the sample preparation process. The CBG cyclization procedure is very simple and workable in estimating this cannabinoid in blood/plasma samples.

GC vs. HPLC in quantitation of CBD, CBG, ∆9-THC and CBN in plasma using different sample preparation methods.

The sensitivity of complex analytical procedures depends not only on the sensitivity of the analytical instrument used, but also on the recovery degree of the examined analyte by the employed sample preparation method. The recovery degrees of individual cannabinoids reported in literature, estimated using the same sample preparation method, are unexpectedly divergent. Therefore, the aim of this study was a thorough assessment of the most commonly used sample preparation methods, such as protein precipitation, LLE, QuEChERS and SPE, in the context of the reliability of the obtained results. The presented report shows that the highest sensitivity, precision and reliability of the chromatographic analysis of CBG, CBD, ∆9-THC and CBN in human plasma can be obtained using SPE. The recovery degrees of these cannabinoids by SPE are highly repeatable and exceed 95 %, while they are significantly lower for such sample preparation methods as protein precipitation, LLE and QuEChERS (ca. 80, 65 and 87, respectively). Moreover, the supernatants obtained by the latter methods contain interferents evoking matrix-effect, which makes reliable quantification of the listed cannabinoids by GC difficult. To our knowledge, the paper is the first such extensive comparison of sample preparation procedures used for the determination of cannabinoids in plasma by GC-MS and HPLC-MS. The presented results and the discussion allow to understand why different recovery degrees for the same xenobiotic can be find in literature despite they have been estimated using the same or different sample preparation method or different chromatography types.

Synthesis and anthelmintic activity of novel thiosemicarbazide and 1,2,4-triazole derivatives: In vitro, in vivo, and in silico study.

INTRODUCTION: Intestinal parasitic infections are neglected diseases and, due to the increasing resistance of parasites to available drugs, they pose an increasing therapeutic challenge. Therefore, there is a great need for finding new compounds with antiparasitic activity. OBJECTIVES: In this work, new thiosemicarbazide and 1,2,4-triazole derivatives were synthesized and tested for their anthelmintic activity. METHODS: The synthesis was carried out by classical methods of organic chemistry. Anthelmintic activity tests were carried out in vitro (Rhabditis sp., Haemonchus contortus, Strongylidae sp.) in vitro (Heligmosomoides polygyrus/bakeri), and in silico analysis was performed. RESULTS: Quinoline-6-carboxylic acid derivative compounds were designed and synthesized. The highest activity in the screening tests in the Rhabditis model was demonstrated by compound II-1 with a methoxyphenyl substituent LC50 = 0.3 mg/mL. In the next stage of the research, compound II-1 was analyzed in the H. contortus model. The results showed that compound II-1 was active and had ovicidal (percentage of dead eggs > 45 %) and larvicidal (percentage of dead larvae > 75 %) properties. Studies in the Strongylidae sp. model confirmed the ovicidal activity of compound II-1 (percentage of dead eggs ≥ 55 %). In vivo studies conducted in the H. polygyrus/bakeri nematode model showed that the number of nematodes decreased by an average of 30 % under the influence of compound II-1. In silico studies have shown two possible modes of action of compound II-1, i.e. inhibition of tubulin polymerization and SDH. The test compound did not show any systemic toxic effects. Its influence on drug metabolism related to the activity of cytochrome CYP450 enzymes was also investigated. CONCLUSION: The results obtained in the in vitro, in vivo, and in silico studies indicate that the test compound can be described as a HIT, which in the future may be used in the treatment of parasitic diseases in humans and animals.

The Anti-Acne Potential and Chemical Composition of Knautia drymeia Heuff. and Knautia macedonica Griseb Extracts.

The treatment of acne and other seborrheic diseases has arisen as a significant clinical challenge due to the increasing appearance of multi-drug resistant pathogens and a high frequency of recurrent lesions. Taking into consideration the fact that some Knautia species are valuable curatives in skin diseases in traditional medicine, we assumed that the thus far unstudied species K. drymeia and K. macedonica may be a source of active substances used in skin diseases. The purpose of this study was to evaluate the antioxidant, anti-inflammatory, antibacterial, and cytotoxic activities of their extracts and fractions. An LC-MS analysis revealed the presence of 47 compounds belonging to flavonoids and phenolic acids in both species while the GC-MS procedure allowed for the identification mainly sugar derivatives, phytosterols, and fatty acids and their esters. The ethanol as well as methanol-acetone-water (3:1:1) extracts of K. drymeia (KDE and KDM) exhibited great ability to scavenge free radicals and good capacity to inhibit cyclooxygenase-1, cyclooxygenase-2, and lipoxygenase. Moreover, they had the most favorable low minimal inhibitory concentration values against acne strains, and importantly, they were non-toxic toward normal skin fibroblasts. In conclusion, K. drymeia extracts seem to be promising and safe agents for further biomedical applications.

Effects of topical dehydroepiandrosterone therapy in women after pelvic organ prolapse surgery.

OBJECTIVE: Pelvic organ prolapse (POP) occurs predominantly in postmenopausal women. Restoration of the proper estrogenization of vaginal mucosa is important in preoperative and postoperative treatment, increasing the effectiveness of this approach. The objective of this study was the development of intravaginal vaginal suppositories containing DHEA and comparison of the clinical effects of vaginal topical therapy with DHEA, estradiol, or antibiotic after POP surgery. METHOD: Nine types of vaginal suppositories containing 6.5 mg DHEA in different bases were prepared to find optimal formulation for the vaginal conditions. Ninety women referred for POP surgery were randomly assigned to one of three groups receiving topical treatment in the postoperative period (estradiol, DHEA, or antibiotic). On admission to hospital and during follow-up vaginal pH, vaginal maturation index and vaginal symptoms were assessed. RESULTS: Vaginal suppositories with the base made from polyethylene glycol 1,000 without surfactants characterized the highest percentage of the released DHEA. In women treated with topical estradiol or DHEA a significant decrease in the number of parabasal cells, increase in superficial and intermediate cells in the vaginal smears, decrease in vaginal pH, and reduction of vaginal symptoms were observed. CONCLUSIONS: The use of topical therapy with DHEA or the use of topical therapy with estradiol in the postoperative period were both shown to improve maturation index, vaginal pH, and vaginal symptoms. The benefits of topical therapy with DHEA after pelvic organ prolapse repair brings similar results as estradiol, without potential systemic exposure to increased concentrations of sex steroids above levels observed in postmenopausal women.

Unexpected formation of dichloroacetic and trichloroacetic artefacts in gas chromatograph injector during Cannabidiol analysis.

The knowledge about the stability of compounds and possible ways of their transformation in the process of sample preparation for analysis and during analysis itself is very helpful in the assessment of possible errors which can appear when an accurate and precise estimation of compound concentration in tested samples is attempted. The present paper shows that a significant amount of CBD present in the blood/plasma sample analyzed by means of GC transforms in the hot GC injector not only to 9α-hydroxyhexahydrocannabinol, 8-hydroxy-iso-hexahydrocannabinol, Δ9-tetrahydrocannabinol, Δ8-tetrahydrocannabinol, and cannabinol but also to the trichloroacetic esters of Δ9-THC and Δ8-THC and, unexpectedly, to their dichloroacetic esters when trichloroacetic acid is used as protein precipitation agent. The increase of GC injector temperature favors the formation of dichloroacetic esters of Δ9-THC and Δ8-THC in relation to their trichloroacetic ones. The appearance of dichloroacetic esters of Δ9-THC and Δ8-THC among CBD transformation products is probably the result of the thermal decomposition of their trichloroacetic esters. The transformation of trichloroacetic derivatives of organic compounds into their dichloroacetic derivatives in GC injector has not been reported yet. The instability of trichloroacetic derivatives of Δ8-/Δ9-THC during their GC analysis is probably accounts for the lack of their GC-MS spectra in the databases. NMR, GC-MS and LC-MS spectra of the newly discovered derivatives constitute an important element of the work. The obtained results demonstrate why the use of trichloroacetic acid for plasma samples deproteinization should be avoided when CBD and/or THC are determined by GC.

Chromatographic analysis of CBD and THC after their acylation with blockade of compound transformation.

METHODS: for the analysis of cannabinoids in bio-matrices are continually improved to achieve best possible sensitivity in their detection and accurate quantification. It has been well documented that CBD cyclizes to Δ9-THC and Δ9-THC isomerizes to Δ8-THC under acidic conditions by means of a Lewis-acid-catalyzed process, causing difficulty in accurate quantification of Δ9-THC in the presence of CBD, of CBD itself and of Δ9-THC itself when these compounds have to be derivatized by acylation. The present paper shows that CBD cyclization and Δ9-THC isomerization can be blocked by tertiary amines or azines, which capture protons appearing in the derivatizing mixture during acylation. The efficiency of the described acylation of CBD depends on the time and temperature of the derivatizing process, whereas the degree of CBD acylation, i.e. the synthesis of mono- or di-acylate CBD derivative, depends on the mutual ratio of the cannabinoid, the acylating agent and the proton binding compound. The way of mono- and di-acyl CBD derivatives formation described in the paper has not been reported yet. The paper contains a comprehensive analytical characterization of two types of CBD acyl derivatives, CBD-TFA and CBD-Ac, obtained by NMR, GC-MS and LC-MS.

Natural vs. artificial cannabinoid oils: the comparison of their antioxidant activities.

In the wide range of products containing hemp ingredients, cannabinoid oils are the most popular. They have gained popularity not only among people struggling with various health ailments, but also those who search for a neutral way of taking care of their body and mind. The antioxidant activities of cannabinoid oils differing in the type of their main cannabinoid [i.e., Cannabigerol (CBG), Cannabidiol (CBD), Δ9-Tetrahydrocannabinol (Δ9-THC), Cannabigerolic acid (CBGA), Cannabidiolic acid (CBDA) or Δ9-Tetrahydrocannabinolic acid (Δ9-THCA)] are compared and discussed in the paper. The oils with the same concentration of their main cannabinoid but prepared in different ways were applied in the experiments. Following the presented results, cannabinoid oils obtained from the plant extracts are characterized by evidently greater antioxidant activity than those prepared from pure cannabinoids. The essential difference in the antioxidant activity of the oils containing the neutral or acidic form of a given cannabinoid is observed only in the case of THC and THCA oils.

Can Extracts from the Leaves and Fruits of the Cotoneaster Species Be Considered Promising Anti-Acne Agents?

This study aimed to evaluate the phenolic profile and biological activity of the extracts from the leaves and fruits of Cotoneaster nebrodensis and Cotoneaster roseus. Considering that miscellaneous species of Cotoneaster are thought to be healing in traditional Asian medicine, we assumed that this uninvestigated species may reveal significant therapeutic properties. Here, we report the simultaneous assessment of chemical composition as well as biological activities (antioxidant, anti-inflammatory, antibacterial, and cytotoxic properties) of tested species. Complementary LC-MS analysis revealed that polyphenols (especially flavonoids and proanthocyanidins) are the overriding phytochemicals with the greatest significance in tested biological activities. In vitro chemical tests considering biological activities revealed that obtained results showed different values depending on concentration, extraction solvent as well as phenolic content. Biological assays demonstrated that the investigated extracts possessed antibacterial properties and were not cytotoxic toward normal skin fibroblasts. Given the obtained results, we concluded that knowledge of the chemical composition and biological activities of investigated species are important to achieve a better understanding of the utilization of these plants in traditional medicine and be useful for further research in their application to treat various diseases, such as skin disorders.

Oleamide as analyte protectant in GC analysis of THC and its metabolites in blood.

Methods for the analysis of cannabinoids in bio-matrices are continually being developed, to achieve a proper sensitivity required for their detection and accuracy in their quantification. The presented paper shows that the analytical sensitivity of GC-MS to THC and its metabolites in blood samples can be significantly increase by oleamide (OLA) addition to the examined sample, which evokes the matrix effect of transient character. The magnitude of signal increment resulting from oleamide presence in the examined sample is the greatest for THC metabolites and depends on oleamide concentration in the examined sample. The use of transient matrix effect to increase the sensitivity of the analysis can be applied not only in QuEChERS procedure, which is applied in the described experiments, but also in other blood sample preparation methods. Evoking the transient matrix effect by means of OLA in the experimental analytical quantitation of THC and its metabolites in blood allowed to lower limit of detection (LOD) approximately by 20.5%, 87.6% and 90.1% in the case of THC, THC-OH and THC-COOH, respectively.

Formation of trifluoroacetic artefacts in gas chromatograph injector during Cannabidiol analysis.

The knowledge of compounds stability in the process of sample preparation for analysis and during analysis itself helps assess the accuracy and precision of estimating their concentration in tested samples. The present paper shows that a significant amount of CBD present in the blood/plasma sample analyzed by means of GC transforms in the hot GC injector not only to 9α-hydroxyhexahydrocannabinol, 8-hydroxy-iso-hexahydrocannabinol, delta-9-tetrahydrocannabinol, Δ8-tetrahydrocannabinol, and cannabinol but also to the trifluoroacetic esters of Δ9-THC and Δ8-THC, when trifuoroacetic acid is used as protein precipitation agent. The amount of those newly revealed CBD transformation products depends on the GC injector temperature and on the extrahent type when extracts of the supernatants centrifuged from human plasma samples are analyzed after their preliminary protein precipitation by trifuoroacetic acid. Although trifuoroacetic acid as a protein precipitating agent has many disadvantages, it is quite often used for this purpose due to its very high protein precipitation efficiency. The results presented in the study demonstrate why the use of trifuoroacetic acid for plasma samples deproteinization should be avoided when CBD is determined by GC.

The Anti-Acne Potential and Chemical Composition of Two Cultivated Cotoneaster Species.

In light of current knowledge on the role of reactive oxygen species and other oxidants in skin diseases, it is clear that oxidative stress facilitates inflammation and is an important factor involved in skin diseases, i.e., acne. Taking into consideration the fact that some Cotoneaster plants are valuable curatives in skin diseases in traditional Asian medicine, we assumed that thus far untested species C. hsingshangensis and C. hissaricus may be a source of substances used in skin diseases. The aim of this study was to evaluate the antioxidant, anti-inflammatory, antimicrobial, and cytotoxic activities of their various extracts. LC-MS analysis revealed the presence of 47 compounds (flavonoids, phenolic acids, coumarins, sphingolipids, carbohydrates), while GC-MS procedure allowed for the identification of 42 constituents (sugar derivatives, phytosterols, fatty acids, and their esters). The diethyl ether fraction of C. hsingshangensis (CHs-2) exhibited great ability to scavenge free radicals and good capacity to inhibit cyclooxygenase-1, cyclooxygenase-2, lipoxygenase, and hyaluronidase. Moreover, it had the most promising power against microaerobic Gram-positive strains, and importantly, it was non-toxic toward normal skin fibroblasts. Taking into account the value of the calculated therapeutic index (>10), it is worth noting that CHs-2 can be subjected to in vivo study and constitutes a promising anti-acne agent.

Synergistic and antagonistic antioxidant effects in the binary cannabinoids mixtures.

From the group of nearly 120 cannabinoids identified in the hemp sativa and marijuana, CBG, CBD, THC and their acidic forms CBGA, CBDA and THCA are the most frequently studied. All these cannabinoids exhibit antioxidant activity manifested in the ability to scavenge free radicals, to prevent the oxidation process and to reduce metal ions. The paper reports and discusses the antioxidant properties of binary mixtures of the mentioned cannabinoids as regards their ability to scavenge free radicals. The paper shows that, depending on cannabinoid type in their binary mixture and their amounts ratio, an additive, synergistic and antagonistic effect of their antioxidant activity is observed. Binary mixtures of the tested cannabinoids in the full range of their molar ratios were used in the experiments. The presented results seems to be essential in terms of more and more numerous reports showing greater pharmacological effectiveness of binary cannabinoid mixtures compared to that of their individual components.

Improving the sensitivity of estimating CBD and other xenobiotics in plasma samples: Oleamide-induced transient matrix effect.

The paper discusses the matrix effect evoked by oleamide (OLA), a compound frequently found in samples processed and/or stored in lab polypropylene vials or disposable syringes. In the case of many substances a higher response for their samples containing OLA than for net solutions is observed. The analyte signal gain resulting from OLA presence in the examined sample depends on the ratio of OLA concentration to analyte concentration. A characteristic feature of the matrix effect evoked by oleamide is its short duration, which makes the chromatographic data (retention value and signal magnitude of examined compound) repeatable and reproducible. The identified "transient matrix effect" may significantly increase the sensitivity of many analytical procedures employing GC. Evoking the transient matrix effect by means of OLA in the experimental analytical quantitation of cannabidiol in plasma allowed to lower its limit of detection (LOD) by more than 50 %.

Effect-directed analysis as a method for quality and authenticity estimation of Rhodiola rosea L. preparations.

Adulterations of food and pharmaceutical preparations are the important global problem. On the one hand, fraud practices are becoming more and more sophisticated while on the other, monitoring and uncovering falsifications are insufficient. One of the most common consumer concern is the quality and authenticity of the purchased products, related to the confidence that they have composition and properties in accordance with the manufacturer's declaration on the label. This refers also to pharmaceuticals potentially delivering great health benefits such as Rhodiola rosea L. supplements. The aim of this study was defining authenticity and possible adulterations of two R. rosea preparations basing on their TLC-bioprofiles and the presence of biomarker compounds characteristic for this plant. The effect-directed analysis (EDA), i.e. TLC hyphenated with micro-chemical and biological assays performed directly on TLC plates followed by HPLC-ESI-MS was used for the bioprofiling of antioxidants, antibacterials, and inhibitors of lipase, acetylcholine, α-glucosidase and tyrosinase as well as for the identification of the biomarkers. The results pointed to the possible adulteration of one of the tested products related to the absence of two rosavins, the most important quality markers of R. rosea.

CBG, CBD, Δ9-THC, CBN, CBGA, CBDA and Δ9-THCA as antioxidant agents and their intervention abilities in antioxidant action.

Positive effect of some cannabinoids in the treatment and prophylaxis of a wide variety of oxidation-associated diseases and growing popularity of supplements containing cannabinoids, mainly cannabinoid oils (e.g. CBD oil, CBG oil), in the self-medication of humans cause a growing interest in the antioxidant properties of these compounds, especially those not showing psychotropic effects. Herein, we report the antioxidant activity of cannabigerol (CBG), cannabidiol (CBD), Δ9-tetrahydrocannabinol (Δ9-THC), cannabinol (CBN), cannabigerolic acid (CBGA), cannabinolic acid (CBDA) and Δ9-tetrahydrocannabinolic acid (Δ9-THCA) estimated by spectrophotometric methods: ABTS, DPPH, ORAC, beta-carotene CUPRAC and FRAP. The presented data prove that all the examined cannabinoids exhibit antioxidant activity manifested in their ability to scavenge free radicals, to prevent the oxidation process and to reduce metal ions. Although the intensity of these activities is not the same for the individual cannabinoids it is comparable for all of them with that of E vitamin. As results from the research, the significance of the two types of electron sources presenting in examined cannabinoids, phenolic groups and double bonds transferring electrons, depends on the type of electron-accepting species - radicals/metal ions.

Conversion of cannabidiol (CBD) to Δ9-tetrahydrocannabinol (Δ9-THC) during protein precipitations prior to plasma samples analysis by chromatography - Troubles with reliable CBD quantitation when acidic precipitation agents are applied.

The growing popularity of supplements containing cannabidiol (CBD), mainly CBD oils, in self-medication of humans and the increased interest in this compound in different preclinical and clinical trials stimulates the development of procedures of CBD analysis in plasma for the study of CBD pharmacology in people and animals or in establishing dose-therapeutic effect relationships of this compound. Preliminary removal of protein by its precipitation from plasma is still one of the willingly applied plasma sample preparation methods in many analytical procedures estimating plasma drug concentration, including CBD. The present paper shows that a significant amount of CBD transforms to Δ9-tetrahydrocannabinol (Δ9-THC) in a hot GC injection system when acidic precipitation agents, such as TFA, TCA, HClO4, H2SO4, ZnSO4 or CHCl3, are used for plasma protein precipitation. The transformation degree depends on the temperature of the GC injector, the concentration of the precipitation agent and the incubation time of plasma with the precipitating agent. At the CBD plasma concentration equal to 50 ng/ml, which is approximately the mean level for patients treated for epileptic syndromes, the CBD transformation degree can exceed 20%. For a reliable estimate of CBD in blood plasma, neutral precipitation agents (e.g. ACN, MeOH, acetone) should be used when plasma deproteinization precedes GC analysis. The presented results are important not only for analysts cooperating with pharmacologists and for medicine doctors examining the activity of CBD-containing drugs in the therapeutic process, but also for forensic scientists who may erroneously find innocent people guilty of using marijuana or its preparations.

Stability of stevioside in food processing conditions: unexpected recombination of stevioside hydrolysis products in ESI source.

Stevioside is the main and the sweetest glycoside of stevia plant. It is attractive as a natural sweetener to diabetics and others on carbohydrate-controlled diets. This paper discusses the stability of stevioside under food processing conditions. It was found that stevioside was transformed not only to rubusoside, steviolbioside, steviol monoside and steviol but also to previously unknown stevioside α-anomer and rubusoside α-anomer. Those two identified stevioside transformation products are formed not only during the heating of acidic, neutral and alkaline stevioside standard solutions and stevia leaves suspensions in water and ethanol/water solvents but also during the processing of foods containing stevia. Apart from presenting the new compounds, the paper additionally shows that the recombination of sugar moiety with steviolbioside molecule in MS/ESI source can occur. The effect of molecule recombination in the MS source is known from the literature; however, it has not been reported previously in relation to stevioside derivatives.

Aqueous and alcoholic adducts of steviol and steviol glycosides in food products containing stevia.

High content of steviol glycosides in stevia leaves is a cause of their high popularity as. a natural sweetener of various sugar-free food products. Stevioside (13-[(2-O-ß-d-glucopyranosyl-ß-d-glucopyranosyl)oxy]-ent-kaur-16-en-19-oic acid ß-d-glucopyranosyl ester) is one of the main steviol glycosides in stevia leaves known for its hydrolytic instability responsible for the formation of simple steviol glucosides (steviolbioside, rubusoside, steviol monoside) and steviol. However, the formation of hydroxy and alkoxy adducts of stevioside and of its hydrolysis products has not yet been reported. The performed experiments prove that water and alkoxy adducts are formed not only during temperature processing of stevioside but also of stevia and stevia-containing food products. Their quantities depend on environment pH, water concentration and food composition. Although they are formed in small amounts their biological activity is unknown and should be recognized.