Update and New Insights on Future Cancer Drug Candidates From Plant-Based Alkaloids.

Cancer is a complex multifactorial disease that results from alterations in many physiological and biochemical functions. Over the last few decades, it has become clear that cancer cells can acquire multidrug resistance to conventional anticancer drugs, resulting in tumor relapse. Thus, there is a continuous need to discover new and effective anticancer drugs. Natural products from plants have served as a primary source of cancer drugs and continue to provide new plant-derived anticancer drugs. The present review describes plant-based alkaloids, which have been reported as active or potentially active in cancer treatment within the past 4 years (2017-2020), both in preclinical research and/or in clinical trials. In addition, recent insights into the possible molecular mechanism of action of alkaloid prodrugs naturally present in plants are also highlighted.

Phytochemical analysis, cytotoxic and antioxidant activities of Myrtus communis essential oil from Morocco.

Background Myrtus communis L. is an aromatic evergreen plant common in Morocco. In addition to its culinary uses, it has been used medicinally as a disinfectant, an antiseptic or as a hypoglycemic agent. However, its cytotoxic activity has not been well investigated so far. The current study describes the chemical composition, cytotoxic and antioxidant activities of Myrtus communis L essential oil obtained from different regions of Morocco. Methods Myrtus communis essential oils were obtained by hydrodistillation, and analyzed by gas chromatography coupled with mass spectrometry. Cytotoxic activity was evaluated in murine mastocytoma P815 and MCF-7 breast cancer cells, using the MTT assay. In addition, DNA fragmentation was assessed by gel electrophoresis. The antioxidant effect was determined by measuring bleaching of ß-carotene with the linoleic acid and the DPPH radical scavenging methods. Results GC-MS analysis showed high amounts of methyl eugenol (18.7%), α-terpineol (15.5%) and geranyl acetate (11.64%) in essential oil from the Benslimane region. In contrast, essential oil from Ouazzane was particularly rich in 1,8-cineole (36.3%). The cytotoxicity results showed that MCF-7 cells were more sensitive than P815 cells to the essential oils from Ouazzane and Benslimane regions with IC50 values of 4 and 6.25 µg/mL, respectively. Moreover, this cytotoxicity was partly associated with DNA fragmentation, which is one of the characteristics of apoptosis. The tested essential oils did not show strong antioxidant activity. Conclusions Myrtus communis L. essential oil exhibits a weak antioxidant effect, but induced remarkable cytotoxic activity by a mechanism related to apoptosis, suggesting a possible application of the bioactive compounds as natural anticancer compounds.

Studies on the Dual Cytotoxicity and Antioxidant Properties of Berberis vulgaris Extracts and Its Main Constituent Berberine.

The present study attempts to investigate the cytotoxic activity of ethanol and ethyl acetate extracts of the Moroccan Berberis vulgaris and its major component berberine, together with exploring their antioxidant properties. It also consists of studying the combination effect of berberine and S-nitroso-N-acetylpenicillamine (SNAP), a nitric oxide (NO) donor, against the human breast adenocarcinoma cell line (MCF-7). Using the MTT assay, we report a differential cytotoxic effect of ethanol and ethyl acetate extracts since the ethanol extract is more cytotoxic than the ethyl acetate one, with IC50 = 3.54 µg/mL and 596.71 µg/mL, respectively. Interestingly, no cytotoxic effect was observed against normal cells. Furthermore, these extracts showed a remarkable antioxidant activity as measured by the DPPH free radicals scavenging assay. In fact, the IC50 values are 69.65 µg/mL and 77.75 µg/mL for the ethanol and ethyl acetate extracts, respectively. In addition, several concentrations of berberine, when combined with the NO donor used at IC30, induced a synergistic cytotoxic activity at concentrations ranging from 8.40 µM to 33.60 µM, as revealed by the combination index values, using the Chou-Talalay method. However, at the other concentrations tested, an antagonistic effect was observed. The observed cytotoxicity was related to apoptosis induction as demonstrated by the annexin-V-streptavidin FITC-staining analysis.

More insights into the pharmacological effects of artemisinin.

Artemisinin is one of the most widely prescribed drugs against malaria and has recently received increased attention because of its other potential biological effects. The aim of this review is to summarize recent discoveries of the pharmaceutical effects of artemisinin in basic science along with its mechanistic action, as well as the intriguing results of recent clinical studies, with a focus on its antitumor activity. Scientific evidence indicates that artemisinin exerts its biological activity by generating reactive oxygen species that damage the DNA, mitochondrial depolarization, and cell death. In the present article review, scientific evidence suggests that artemisinin is a potential therapeutic agent for various diseases. Thus, this review is expected to encourage interested scientists to conduct further preclinical and clinical studies to evaluate these biological activities.

Chemical Composition and Cytotoxic and Antibacterial Activities of the Essential Oil of Aloysia citriodora Palau Grown in Morocco.

The aim of this work is to investigate the in vitro cytotoxic and antibacterial effects of the essential oils of Aloysia citriodora Palau, harvested in different regions of Morocco. The chemical profile was established using gas chromatography-mass spectrometry analysis. The cytotoxic activity against P815, MCF7, and VERO cell lines as well as the normal human peripheral blood mononuclear cells (PBMCs) was evaluated using the MTT assay. Standard, ATCC, strains of bacteria (Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa) were cultivated in Muller Hinton media. Then, agar disc diffusion, minimum inhibitory concentrations (MICs), and minimal bactericidal concentrations (MBCs) were determined using microdilution method. The essential oils obtained were predominantly composed of ß-spathulenol (15.61%), Ar-curcumene (14.15%), trans-caryophyllene oxide (14.14%), and neral (10.02%). The results of the assays showed that the cytotoxic effect of the essential oil of A. citriodora was high on P815 and moderate on MCF7 and on VERO cell lines. However, no cytotoxic effect was observed on PBMCs. On the other hand, essential oils showed a significant antimicrobial activity against both Gram-negative and Gram-positive bacteria. MICs ranged between 2.84 and 8.37 mg/ml. Essential oil of A. citriodora leaves possesses significant antibacterial effect and cytotoxic activity against tumor cell lines.

Differential Cytotoxic Activity of Essential Oil of Lippia citriodora from Different Regions in Morocco.

The aim of this work was to investigate the cytotoxic effect of the essential oil of dried leaves of Lippia citriodora (H.B. & K.) harvested in different regions of Morocco. This effect was evaluated against the P815 murine mastocytoma cell line using the MTT assay. Interestingly, this work demonstrated for the first time that these essential oils exhibited a strong cytotoxic activity against the P815 cell line, with IC50 values ranging from 7.75 to 13.25 µg/ml. This cytotoxicity began early and increased in a dose- and time-dependent manner. The chemical profile of these essential oils was analyzed by gas chromatography coupled to mass spectrometry. Importantly, the difference in terms of major components' contents was not significant suggesting probably that the differential cytotoxicity between these essential oils could be attributed to the difference in the content of these essential oils in minor compounds, which could interact with each other or with the main molecules. Finally, this study demonstrated for the first time that essential oils of L. citriodora from different regions in Morocco induced apoptosis against P815 tumor cell line.

Comparative Phytochemical Analysis of Essential Oils from Different Biological Parts of Artemisia herba alba and Their Cytotoxic Effect on Cancer Cells.

PURPOSE: Carrying out the chemical composition and antiproliferative effects against cancer cells from different biological parts of Artemisia herba alba. METHODS: Essential oils were studied by gas chromatography coupled to mass spectrometry (GC-MS) and their antitumoral activity was tested against P815 mastocytoma and BSR kidney carcinoma cell lines; also, in order to evaluate the effect on normal human cells, oils were tested against peripheral blood mononuclear cells PBMCs. RESULTS: Essential oils from leaves and aerial parts (mixture of capitulum and leaves) were mainly composed by oxygenated sesquiterpenes 39.89% and 46.15% respectively; capitulum oil contained essentially monoterpenes (22.86%) and monocyclic monoterpenes (21.48%); esters constituted the major fraction (62.8%) of stem oil. Essential oils of different biological parts studied demonstrated a differential antiproliferative activity against P815 and BSR cancer cells; P815 cells are the most sensitive to the cytotoxic effect. Leaves and capitulum essential oils are more active than aerial parts. Interestingly, no cytotoxic effect of these essential oils was observed on peripheral blood mononuclear cells. CONCLUSION: Our results showed that the chemical composition variability of essential oils depends on the nature of botanical parts of Artemisia herba alba. Furthermore, we have demonstrated that the differential cytotoxic effect depends not only on the essential oils concentration, but also on the target cells and the botanical parts of essential oils used.

Differential effect of artemisinin against cancer cell lines.

The present study aims at defining the differential cytotoxicity effect of artemisinin toward P815 (murin mastocytoma) and BSR (kidney adenocarcinoma of hamster) cell lines. Cytotoxicity was measured by the growth inhibition using MTT assay. These in vitro cytotoxicity studies were complemented by the determination of apoptotic DNA fragmentation and Annexin V- streptavidin-FITC assay. Furthermore, we examined the in vitro synergism between artemisinin and the chemotherapeutic drug, vincristin. The in vivo study was investigated using the DBA2/P815 (H2d) mouse model. While artemisinin acted on both tumor cell lines, P815 was much more sensitive to this drug than BSR cells, as revealed by the respective IC50 values (12 µM for P815 and 52 µM for BSR cells). On another hand, and interestingly, apoptosis was induced in P815 but not induced in BSR. These data, reveal an interesting differential cytotoxic effect, suggesting the existence of different molecular interactions between artemisinin and the studied cell lines. In vivo, our results clearly showed that the oral administration of artemisinin inhibited solid tumor development. Our study demonstrates that artemisinin caused differential cytotoxic effects depending not only on the concentration and time of exposure but also on the target cells.

Comparative study of the antitumor effect of natural monoterpenes: relationship to cell cycle analysis

Monoterpenes have been identified as responsible of important therapeutic effects of plant-extracts. In this work, we try to compare the cytotoxic effect of six monoterpenes (carvacrol, thymol, carveol, carvone, eugenol and isopulegol) as well as their molecular mechanisms. The in vitro antitumor activity of the tested products, evaluated against five tumor cell lines, show that the carvacrol is the most cytotoxic monoterpene. The investigation of an eventual synergistic effect of the six natural monoterpenes with two anticancer drugs revealed that there is a significant synergy between them (p<5%). On the other hand, the effect of the tested products on cell cycle progression was examined by flow cytometry after DNA staining in order to investigate the molecular mechanism of their cytotoxic activity. The results revealed that carvacrol and carveol stopped the cell cycle progression in S phase; however, thymol and isopulegol stopped it in G0/G1 phase. Regarding carvone and eugenol, no effect on cell cycle was observed.

Evaluation of the in vitro and in vivo anticancer properties of Moroccan propolis extracts

This investigation aimed to evaluate the in vitro and in vivo antitumor potential of a Moroccan propolis extracts. For in vitro assays, three mammalian tumor cell lines were used: BSR (hamster renal adenocarcinoma), Hep-2 (human laryngeal carcinoma) and P815 (murin mastocytoma). The propolis ethanolic extract as well as the ethyl acetate extract, exert an in vitro cytotoxic activity in dose-dependent manner. The IC50 values were ranging from 15 µg/mL to 38 µg/mL. This activity depends not only on the extract's chemical composition (analysed by HPLC/ESI-MS), but also on the target tumor cells. Interestingly, the cytotoxic effect of these extracts on the normal human peripheral blood mononuclear cells (PBMC) was weak when compared to that induced on tumor cells. On the other hand, oral route treatment of P815 tumor-bearing mice (DBA2/P815) with propolis ethanolic extract (5 mg per mouse every fourth day, five times for group A, and 2.5 mg per mouse every fourth day, five times for group B) significantly reduced the tumor volume (1.2 cm³ for group A and 2.7 cm³ for group B at the 22nd day after tumor graft). These effects are statistically significant as compared to those obtained with the control untreated mice (tumor volume 3.5 cm³ at day 22).

Chemical composition and antiproliferative activity of essential oil from aerial parts of a medicinal herb Artemisia herba-alba

Artemisia herba-alba Asso., Asteraceae, is widely used in Morrocan folk medicine for the treatment of different health disorders. However, no scientific or medical studies were carried out to assess the cytotoxicity of A. herba-alba essential oil against cancer cell lines. In this study, eighteen volatile compounds were identified by GC-MS analysis of the essential oil obtained from the plant's aerial parts. The main volatile constituent in A. herba-alba was found to be a monoterpene, Verbenol, contributing to about 22 percent of the total volatile components. The essential oil showed significant antiproliferative activity against the acute lymphoblastic leukaemia (CEM) cell line, with 3 µg/mL as IC50 value. The anticancer bioactivity of Moroccan A. herba-alba essential oil is described here for the first time.

Chemical composition and antitumor activity of different wild varieties of Moroccan thyme

Many species of Thyme have been widely used in Moroccan folk medicine as anti-inflammatory, antioxidant and antinociceptive agents. This study was designed to examine the chemical composition and the in vitro antitumor activity of the essential oils and various extracts of thyme species collected in different regions of Morocco. The essential oil, obtained by hydrodistillation, and the various extracts, obtained by Soxhlet extraction, using solvents of varying polarity, were analysed by gas chromatography coupled to mass spectrometry (GC-MS). Both major and trace components were analysed. Overall, the major constituents in the chemical composition of Moroccan thyme populations were carvacrol, thymol, borneol and p-cymene. The rate of these components can hit respectively to 85 percent, 42 percent, 59 percent, and 23 percent. Furthermore, the essential oils as well as two pure products (carvacrol and thymol) were tested for their antitumoral activity against P815 mastocytoma cell line. While all these products showed a dose dependent cytotoxic effect, the carvacrol was the most cytotoxic one compared to the others. Interestingly, when these products were tested against the normal human peripheral blood mononuclear cells, they show a proliferative effect instead of a cytotoxic one.

Muitas espécies de Tomilho têm sido amplamente utilizadas na medicina popular morroquina como agentes antiinflamatório, antioxidante e antinociceptivo. Este estudo foi realizado para analisar a composição química e a atividade antitumoral in vitro dos óleos essenciais e de vários extratos de espécies de tomilho coletadas em diferentes regiões do Marrocos. O óleo essencial, obtido através de hidrodestilação, e os vários extratos, obtidos por extração em aparelho de Soxhlet, utilizando solventes de diferentes polaridades, foram analisados através de cromatografia gasosa acoplada à espectrometria de massas (CG/EM). Tanto os componentes majoritários quanto os minoritário foram analisados. De um modo geral, os constituintes principais da composição química das populações de tomilho morroquinas foram carvacrol, timol, borneol e p-cimeno. A quantidade desses componentes pode ser de 85 por cento, 42 por cento, 59 por cento, e 23 por cento, respectivamente. Em adição, os óleos essenciais bem como dois produtos puros (carvacrol e timol) foram testados quanto à sua atividade antitumoral contra mastocitoma da linhagem P815. Enquanto todos esses produtos mostraram efeito citotóxico dependente da dose, o carvacrol foi o mais citotóxico quando comparado aos outros. Interessantemente, quando estes produtos foram testados contra células mononucleares sangüíneas periféricas humanas normais, mostraram efeito proliferativo em vez de citotóxico.