Exploring the chemical and bioactive properties of Hibiscus sabdariffa L. calyces from Guinea-Bissau (West Africa).

Different external factors influence the chemical characteristics of natural products, varying according to the geographic origin. The present study determined the nutritional and chemical composition of Hibiscus sabdariffa L. dried calyces (Guinea-Bissauan origin), as well as the phenolic composition, antioxidant, anti-inflammatory, cytotoxicity and antimicrobial activity of its infusion and hydroethanolic extracts. Among the chemical components, glucose and quinic acid showed the major concentration for sugars and organic acids, respectively. Palmitic acid and α-tocopherol were the most abundant lipophilic compounds. The individual phenolic compounds were analysed through HPLC-DAD-ESI/MS. Thirteen compounds were identified in the hydroethanolic extract, while twelve were identified in the infusion, 3-O-caffeoylquinic acid being the major non-anthocyanin compound. Three anthocyanins were identified, delphinidin-3-O-sambubioside being the most abundant. Both extracts showed promising results in all the bioactive assays. This study exhibited the beneficial properties of H. sabdariffa and also emphasized the potential applications of this plant in different industrial sectors.

Optimization of heat- and ultrasound-assisted extraction of anthocyanins from Hibiscus sabdariffa calyces for natural food colorants.

Heat- and ultrasound-assisted extraction methods were applied to recover anthocyanins from Hibiscus sabdariffa calyces. The extraction variables, time (t), ethanol proportion (S), and temperature (T) or ultrasonic power (P), were combined in a 5-level experimental design and analysed by response surface methodology for process optimization. The delphinidin-3-O-sambubioside (C1) and cyanidin-3-O-sambubioside (C2) levels were monitored by LC-DAD-ESI/MSn and used as response criteria. The developed models were successfully fitted to the experimental data and used to determine optimal extraction conditions. UAE was the most efficient method yielding 51.76 mg C1 + C2/g R under optimal conditions (t = 26.1 min, P = 296.6 W and S = 39.1% ethanol, v/v). The dose-response effects of the solid/liquid ratio on the extraction rate were also determined. The anthocyanin levels herein reported are higher than those found in the literature, which support the potential use of H. sabdariffa as a sustainable source of natural colorants with application in different industrial sectors.

Hibiscus sabdariffa L. as a source of nutrients, bioactive compounds and colouring agents.

The nutritional and bioactive composition of plants have aroused much interest not only among scientists, but also in people's daily lives. Apart from the health benefits, plants are a source of pigments that can be used as natural food colorants. In this work, the nutritional composition of Hibiscus sabdariffa L. was analysed, as well as its bioactive compounds and natural pigments. Glucose (sugar), malic acid (organic acid), α-tocopherol (tocopherol) and linoleic acid (fatty acid) were the major constituents in the corresponding classes. 5-(Hydroxymethyl) furfural was the most abundant non-anthocyanin compound, while delphinidin-3-O-sambubioside was the major anthocyanin both in its hydroethanolic extract and infusion. H. sabdariffa extracts showed antioxidant and antimicrobial activities, highlighting that the hydroethanol extract presents not only lipid peroxidation inhibition capacity, but also bactericidal/fungicidal inhibition ability for all the bacteria and fungi tested. Furthermore, both extracts revealed the absence of toxicity using porcine primary liver cells. The studied plant species was thus not only interesting for nutritional purposes but also for bioactive and colouring applications in food, cosmetic and pharmaceutical industries.

Contribution of the phenolic composition to the antioxidant, anti-inflammatory and antitumor potential of Equisetum giganteum L. and Tilia platyphyllos Scop.

Naturally-occurring phytochemicals have received pivotal attention in the last few years, due to the increasing evidence of biological activities. Thus, in the present study, the antioxidant, anti-inflammatory and antitumor potentials of hydroethanolic extracts rich in phenolic compounds obtained from Equisetum giganteum L. and Tilia platyphyllos Scop. were assessed and directly correlated with their content of phenolic compounds, by using HPLC-DAD-ESI/MS analysis. T. platyphyllos showed the higher bioactive potential, evaluated in terms of antioxidant (radical scavenging effects - 105 µg mL-1, reducing power - 123 µg mL-1, ß-carotene bleaching inhibition - 167 µg mL-1, and lipid peroxidation inhibition - 56 µg mL-1), anti-inflammatory (225 µg mL-1 inhibited 50% of nitric oxide production) and antitumor (breast - 224 µg mL-1; lung - 247 µg mL-1; cervical - 195 µg mL-1 and hepatocellular - 173 µg mL-1 carcinoma cells) activity, without having cytotoxic effects (>400 µg mL-1). These biological properties were positively correlated with its content and composition of phenolic compounds. Flavonoid contents were markedly higher than the content of phenolic acids, in both samples, being respectively 50.4 mg g-1 and 11.65 mg g-1 for T. platyphyllos, and 21.7 mg g-1 and 4.98 mg g-1 for E. giganteum. Moreover, while in E. giganteum extract, kaempferol-O-glucoside-O-rutinoside was the most abundant flavonoid, in T. platyphyllos extract protocatechuic acid and (-)-epicatechin were the most abundant phenolic acid and flavonoid, respectively. In relation to their content of phenolic acids, protocatechuic and caffeic acids existed in higher abundance in T. platyphyllos and E. giganteum hydroethanolic extracts, respectively. However, it would be interesting to evaluate the in vivo efficacy of both plant extracts to unveil the involved modes of action and to establish effective therapeutic doses.

Bioactive properties and functional constituents of Hypericum androsaemum L.: A focus on the phenolic profile.

Hypericum androsaemum L. ethanol:water extract acted as a lipid peroxidation inhibitor and free radical scavenger. A marked inhibition of the growth of breast, lung, cervical and hepatocellular human carcinoma cell lines was also observed, whereas no toxicity was shown against non-tumor porcine liver cells (>400µg/mL). The extract was also effective in inhibiting nitric oxide production, as an indicator of the anti-inflammatory potential. The anti-Candida effects varied among different strains of the same species, C. glabrata and C. tropicalis being the most sensible species with an effect directly related with the extract concentrations tested. A significant anti-biofilm formation potential was also observed, namely for C. glabrata and C. tropicalis (biofilm reduction >90%). 5-O-Caffeoylquinic and 3-O-caffeoylquinic acids were the most abundant phenolic compounds identified in the extract, and might be related with the observed bioactive effects. Nevertheless, future studies should be carried out to obtain dose-response curves of the isolated active compounds, in order to perform further pre-clinically testing to quantify the presence of the most active compounds in the extract.