Solamargine, a bioactive steroidal alkaloid isolated from Solanum aculeastrum induces non-selective cytotoxicity and P-glycoprotein inhibition.

BACKGROUND: Solanum aculeastrum fruits are used by some cancer sufferers as a form of alternative treatment. Scientific literature is scarce concerning its anticancer activity, and thus the aim of the study was to assess the in vitro anticancer and P-glycoprotein inhibitory potential of extracts of S. aculeastrum fruits. Furthermore, assessment of the combinational effect with doxorubicin was also done. METHODS: The crude extract was prepared by ultrasonic maceration. Liquid-liquid extraction yielded one aqueous and two organic fractions. Bioactive constituents were isolated from the aqueous fraction by means of column chromatography, solid phase extraction and preparative thin-layer chromatography. Confirmation of bioactive constituent identity was done by nuclear magnetic resonance and ultra-performance liquid chromatography mass spectrometry. The crude extract and fractions were assessed for cytotoxicity and P-glycoprotein inhibition in both cancerous and non-cancerous cell lines using the sulforhodamine B and rhodamine-123 assays, respectively. RESULTS: Both the crude extract and aqueous fraction was cytotoxic to all cell lines, with the SH-SY5Y neuroblastoma cell line being most susceptible to exposure (IC50 = 10.72 µg/mL [crude], 17.21 µg/mL [aqueous]). Dose-dependent P-glycoprotein inhibition was observed for the crude extract (5.9 to 18.9-fold at 100 µg/mL) and aqueous fraction (2.9 to 21.2 at 100 µg/mL). The steroidal alkaloids solamargine and solanine were identified. While solanine was not bioactive, solamargine displayed an IC50 of 15.62 µg/mL, and 9.1-fold P-glycoprotein inhibition at 100 µg/mL against the SH-SY5Y cell line. Additive effects were noted for combinations of doxorubicin against the SH-SY5Y cell line. CONCLUSIONS: The crude extract and aqueous fraction displayed potent non-selective cytotoxicity and noteworthy P-glycoprotein inhibition. These effects were attributed to solamargine. P-glycoprotein inhibitory activity was only present at concentrations higher than those inducing cytotoxicity, and thus does not appear to be the likely mechanism for the enhancement of doxorubicin's cytotoxicity. Preliminary results suggest that non-selective cytotoxicity may hinder drug development, however, further assessment of the mode of cell death is necessary to determine the route forward.

Effect of the aqueous extract of the aerial parts of Monsonia angustifolia E. Mey. Ex A. Rich., on the sexual behaviour of male Wistar rats.

BACKGROUND: Monsonia angustifolia (Geraniaceae) is a medicinal plant traditionally used in South Africa to increase libido and to treat erectile dysfunction. METHODS: In-vivo aphrodisiac activities of the crude extracts of the plant prepared in water at 3, 30 and 300 mg/kg body weight were evaluated for 7 days using sildenafil citrate (Viagra) and 1% ethanol in distilled water as positive and negative controls respectively. Male rats were selected and monitored in each group for sexual behaviour by exposing them to sexually receptive females on days 1, 3 and 7 for 60 minutes each between 7:00 pm and 3:00 am. The following male sexual parameters were observed: Mount Frequency (MF), Intromission Frequency (IF), Mount Latency (ML), Intromission Latency (IL), Ejaculation Frequency (EF), Ejaculatory Latency (EL) and Post-Ejaculatory Interval (PEI). RESULTS: The administration of the extract resulted in significant increase (p < 0.05) in mount frequency, intromission frequency, ejaculation frequency, ejaculation latency and serum hormone concentrations. The computed indices of sexual behaviour such as erection, quick flips, long flips and total penile reflexes were also increased. However, the mount latency, intromission latency and post ejaculation interval were significantly decreased throughout the experimental period. The administration of 300 mg/kg body weight of the aqueous extract produced the best effects in all the parameters. CONCLUSION: Generally, the extract of Monsonia angustifolia produced pro-sexual stimulatory effects in the male rats especially when administered at 300 mg/kg body weight. The results validate the use of the plant by the indigenous people to increase libido and treat premature ejaculation and erectile dysfunction in males.

Structure-activity relationship study of sesquiterpene lactones and their semi-synthetic amino derivatives as potential antitrypanosomal products.

Sesquiterpene lactones (STLs) are natural products that have potent antitrypanosomal activity in vitro and, in the case of cynaropicrin, also reduce parasitemia in the murine model of trypanosomiasis. To explore their structure-antitrypanosomal activity relationships, a set of 34 natural and semi-synthetic STLs and amino-STLs was tested in vitro against T. b. rhodesiense (which causes East African sleeping sickness) and mammalian cancer cells (rat bone myoblast L6 cells). It was found that the α-methylene-γ-lactone moiety is necessary for both antitrypanosomal effects and cytotoxicity. Antitrypanosomal selectivity is facilitated by 2-(hydroxymethyl)acrylate or 3,4-dihydroxy-2-methylenebutylate side chains, and by the presence of cyclopentenone rings. Semi-synthetic STL amines with morpholino and dimethylamino groups showed improved in vitro activity over the native STLs. The dimethylamino derivative of cynaropicrin was prepared and tested orally in the T. b. rhodesiense acute mouse model, where it showed reduced toxicity over cynaropicrin, but also lost antitrypanosomal activity.

Antiprotozoal isoflavan quinones from Abrus precatorius ssp. africanus.

A library of 206 extracts from selected South African plants was screened in vitro against a panel of protozoan parasites, Plasmodium falciparum, Trypanosoma brucei rhodesiense, and Leishmania donovani. A CH2Cl2/MeOH (1 : 1) extract of Abrus precatorius L. ssp. africanus strongly inhibited P. falciparum (98 %), T. b. rhodesiense (100 %), and L. donovani (76 %) when tested at a concentration of 10.0 µg/mL. The active constituents were tracked by HPLC-based activity profiling and isolated by preparative and semipreparative RP-HPLC chromatography. Structures were established by HR-ESIMS, and 1D and 2D NMR (1H, 13C, COSY, HMBC, HSQC, and NOE difference spectroscopy). Five compounds were obtained and identified as two isoflavan hydroquinones, abruquinone H (1) and abruquinone G (2), and three isoflavan quinones, abruquinone I (3), abruquinone B (4), and 7,8,3''5'-tetramethoxyisoflavan-1',4'-quinone (5). Compounds 1 and 3 were new natural products. The absolute configuration of compounds was determined by comparison of electronic circular dichroism spectra with calculated ECD data. Compounds 3 and 4 showed strong activity against T. b. rhodesiense (IC50 values of 0.30 and 0.16 µM, respectively) and good selectivity (selectivity indices of 73.7 and 50.5, respectively).

Antiprotozoal screening of 60 South African plants, and the identification of the antitrypanosomal germacranolides schkuhrin I and II.

Two hundred and seven extracts were prepared from sixty plants from South Africa and screened for in vitro activity against Trypanosoma brucei rhodesiense, Trypanosoma cruzi, Leishmania donovani, and Plasmodium falciparum. For the 21 extracts which inhibited the growth of one or more parasites with more than 95 % at 10 µg/mL, the IC50 values against all four protozoal parasites and cytotoxic IC50 values against L6 myoblasts were determined. Amongst the most notable results are the activities of Psoralea pinnata (IC50 of 0.15 µg/mL), Schkuhria pinnata (2.04 µg/mL), and Vernonia mespilifolia (1.01 µg/mL) against Trypansoma brucei rhodesiense. HPLC-based activity profiling was used to identify the active constituents in the extracts, and the germacranolide sesquiterpene lactones schkuhrin I and II from S. pinnata, and cynaropicrin from V. mespilifolia were identified, with IC50 values of 0.9, 1.5, and 0.23 µM, respectively.

In vitro determination of the anti-aging potential of four southern African medicinal plants.

BACKGROUND: Aging is an inevitable process for all living organisms. During this process reactive oxygen species generation is increased which leads to the activation of hyaluronidase, collagenase and elastase, which can further contribute to skin aging. Four southern African medicinal plants; Clerodendrum glabrum, Schotia brachypetala, Psychotria capensis and Peltophorum africanum, were investigated to assess their anti-aging properties. METHODS: Anti-elastase, anti-collagenase and anti-hyaluronidase activities of twenty-eight samples, consisting of methanol and ethyl acetate extracts of the four plants, were determined using spectrophotometric methods. Radical scavenging activity was determined by the ability of the plant extracts to scavenge the ABTS•+ radical. RESULTS: The majority of the samples in the anti-elastase assay and nine in the anti-collagenase assay showed more than 80% inhibition. The ethyl acetate extract of S. brachypetala bark and leaves of P. capensis inhibited elastase activity by more than 90%. The methanol extract of S. brachypetala bark contained the highest anti-hyaluronidase activity (75.13 ± 7.49%) whilst the ethyl acetate extract of P. africanum bark exhibited the highest antioxidant activity (IC50: 1.99 ± 0.23 µg/ml). CONCLUSION: The free radical scavenging activity and enzyme inhibitory activity of the plant extracts investigated suggests that they can help restore skin elasticity and thereby slow the wrinkling process. P. africanum was the plant with the most promising activity and will be subjected to further testing and isolation of the active compound/s.

Antifungal and antibacterial activity and chemical composition of polar and non-polar extracts of Athrixia phylicoides determined using bioautography and HPLC.

BACKGROUND: Athrixia phylicoides DC. (Asteraceae) is used medicinally in South Africa to treat a plethora of ailments, including heart problems, diabetes, diarrhoea, sores and infected wounds. It is also prepared in the form of a tea (hot decoction) taken as a refreshing, pleasant-tasting beverage with commercialization potential. METHODS: Extracts of the dried ground aerial parts were prepared using organic solvents (diethyl ether, dichloromethane/methanol, ethyl acetate and ethanol) and water. These extracts were subjected to HPLC, TLC and bioautography analysis with the aim of linking a range of peaks visualized in HPLC chromatography profiles to antibacterial and antifungal activity of the same extracts. RESULTS: HPLC revealed a group of compounds extracted by more than one solvent. Compounds identified include inositol, caffeic acid, quercetin, kaempferol, apigenin, hymenoxin and oleanolic acid. The organic extracts displayed similar TLC profiles, and bioautography indicated approximately five antibacterial compounds, but only two antifungal compounds in these extracts. Bioautography indicated that cold water extracted the least antimicrobial compounds. CONCLUSIONS: Several previously unknown compounds were identified in Athrixia phylicoides extracts, and bioautography indicated a number of antibacterial and antifungal compounds. There were notable differences in chemical composition and bioactivity between the organic and aqueous extracts. Further research is necessary to fully characterize the active components of the extracts.

Ethnomedicinal Uses, Phytochemistry and Pharmacological Properties of Suregada Genus: A Review.

Plants of the Suregada Roxb. ex Rottler (formerly Gelonium Roxb. ex Willd) are utilized to treat various ailments, namely, hepatic, gum diseases, pyrexia, eczema, and venereal diseases. This review links the reported compounds to ethnomedicinal uses through pharmacological activities. The compounds possess anticancer, anti-allergic, antibacterial, anti-inflammatory, antioxidant, and anti-HIV properties. From the previous reports, 32 known species of the Suregada genus have been investigated morphologically, and nine were investigated for their phytochemistry and pharmacology. Phytochemistry, ethnomedicinal, and pharmacological uses of the other 23 Suregada species are not known and/or not reported. In this review, abietane diterpenoids are the main compounds expressed by the Suregada, accounting for 71 of the 114 reported compounds. Ten triterpenoids and sterols, one aliphatic, two lignans, five flavonoids, and twenty-one nitrogen-containing compounds have been reported from the genus.

Cytotoxicity and antimicrobial activity of isolated compounds from Monsonia angustifolia and Dodonaea angustifolia.

ETHNOPHARMACOLOGICAL RELEVANCE: Monsonia angustifolia is traditionally used to treat anthrax, heartburn, diarrhea, eye infections and hemorrhoids. Dodonaea angustifolia is frequently used as a treatment for dental pain, microbial infections and jungle fever. The two plant species were selected due to the presence of secondary metabolites such as coumarins, flavonoids, terpenoids, saponins and polyphenolics from the crude extracts, which exhibit pharmacological significance. The pure isolated compounds from the crude extracts are known for their diverse structures and interesting pharmacophores. AIM: To isolate and identify antibacterial and antifungal chemical constituents from Monsonia angustifolia and Dodonaea angustifolia plant extracts and evaluate the cytotoxicity of pure compounds from the crude extracts. MATERIALS AND METHODS: Extractives from M. angustifolia and D. angustifolia plants were isolated using chromatographic techniques and structures were elucidated based on NMR, IR and MS spectroscopic techniques. A microplate serial dilution method was used to evaluate the antibacterial activity of extracts and pure compounds against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and antifungal activity against Candida albicans and Cryptococcus neoformans. The cytotoxicity was determined using the 3-(4, 5-dimethylthiazol)-2, 5-diphenyl tetrazolium bromide (MTT) assay. RESULTS: The dichloromethane, ethyl acetate and methanol crude extracts from the plants exhibited significant inhibition of microbial growth. The phytochemical investigation of these active crude extracts led to the isolation of five pure active compounds, 5-methoxyjusticidin A (1), cis-phytyl diterpenoidal fatty acid ester (2), stigmasterol (3), ß-sitosterol (4) and 5-hydroxy-7,4'-dimethoxyflavone (5). Stigmasterol (3) showed good antifungal activity against Cryptococcus neoformans with a minimum inhibition concentration (MIC) of 25 µg/mL and Candida albicans (MIC = 50 µg/mL). CONCLUSION: Compounds (1-5) isolated from Monsonia angustifolia and Dodonaea angustifolia showed antibacterial and antifungal activities and were non-toxic against Madin-Darby canine kidney (MDCK) cells and VERO monkey kidney (VERO) cells.

Investigating the Toxicity of Compounds Yielded by Staphylococci on Vero Cells.

Bacterial secondary metabolites play a major role in the alleviation of diseases; however, the cytotoxicity of other metabolites cannot be ignored as such metabolites could be detrimental to human cells. Three Staphylococci strains Staphylococcus aureus, staphylococcus epidermidis and staphylococcus saprophyticus were used in the experiments. These strains are well known to cause hospital and community-acquired infections. Secondary metabolites from S. aureus isolated from milk of cows with clinical features of mastitis (swollen udders and the production of watery clotted milk), S. saprophyticus (ATCC 35552), and S. epidermidis (ATCC 51625) were exposed to a minimal medium then screened using Gas Chromatography High-Resolution Time-of-flight Mass Spectrometry (GC-HRTOF-MS) and identified with Nuclear Magnetic Resonance (NMR). From S. epidermidis, two compounds were isolated: oleamide and methyl palmitate; three from S. aureus, including fluoranthene, 3-methyl-2-phenyl-1H-pyrrole, and cyclo(L-Leu-L-Propyl); while S. saprophyticus yielded succinic acid, 1,2,6-hexantriol, veratramine, and 4-methyl-pentyl-amine. The secondary metabolites were tested for cytotoxicity using the Vero cell line. Fluoranthene exhibited toxicity with an LC50 of 0.0167 mg/mL to Vero cells, while the other metabolites did not. Methyl palmitate was the least toxic of all of the metabolites. The results imply that none of the compounds, except fluoranthene, pose any danger to human cells.