Isoflavones from Calpurnia Aurea subsp. aurea and their anticancer activity.

BACKGROUND: Calpurnia aurea is an African medicinal plant used in many countries in Africa to treat a range of medical conditions or disorders. Extracts of the plant were shown to be active in antibacterial and antioxidant assays as well as against lice, ticks and maggots. The aim of the study was to isolate the phytochemical constituents from the plant and to test them in appropriate bioassays dependent on the compounds isolated in order to provide a rationale for the use of the plant in ethno-medicine or to provide some information on its constituents. MATERIALS AND METHODS: The stem and bark of the plant was extracted with organic solvents of varying polarity and the extracts separated and purified using column chromatography. The isolated compounds were identified by NMR spectroscopy and the compounds were tested for their in vitro anticancer activity against breast (MCF7), renal (TK10) and melanoma (UACC62) human cell lines using an in house method developed at the CSIR, South Africa. RESULTS: The isoflavones, 4',5,7-trihydroxyisoflavone (1), 7,3'-dihydroxy-5'-methoxyisoflavone (2), 7-hydroxy-4',8-dimethoxyisoflavone (3), 7-acetoxy-4',8-dimethoxyisoflavone (4) and 3',7-dihydroxy-4',8-dimethoxyisoflavone (5), a pterocarpan (3-acetoxy-9-methoxypterocarpan) and a quinolizidine alkaloid (calpurnine) were isolated from the stem and bark of Calpurnia aurea. The tetrasubstituted isoflavone 5 was found to be the most active in the three cell lines amongst all the compounds tested. This was followed by trisubstituted isoflavone 2. CONCLUSION: The isoflavones showed moderate activity against the renal, melanoma and breast cancer cell lines tested against, with the isoflavones 2 and 5 showing the best activity of the compounds tested. These isoflavones may have a synergistic effect with other anticancer drugs.

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.

Quinolizidine alkaloids from Sophora velutina subsp. zimbabweensis (Fabaceae: Sophoreae).

Three novel quinolizidine alkaloids, N-methylenehydroxycytisine (1), 6,7-dihydroxylupanine (2), and velutinine (3) have been isolated from the fruits and pods (1 and 2) and stem bark (3) of Sophora velutina subsp. zimbabweensis along with the known quinolizidine alkaloids, 7-hydroxylupanine (4), thermopsine (5), N-methylcytisine (6), cytisine (7), an aromatic ester, methyl-3-(3',4'-dimethoxyphenyl)-2-propenoate (8) and the triterpenoids, lup-20(29)-ene-3beta-ol (9) and 12-oleanen-3-one (10). Compounds 6 and 10 showed good antibacterial activity against E. faecalis, with MIC values of 20.8 and 10.9 microg mL(-1), respectively. The other compounds tested exhibited low to moderate antibacterial activity.

The antimicrobial, antioxidative, anti-inflammatory activity and cytotoxicity of different fractions of four South African Bauhinia species used traditionally to treat diarrhoea.

ETHNOPHARMACOLOGICAL IMPORTANCE: Many Bauhinia species, including those indigenous to South Africa, are used in traditional medicine across the world for treating ailments such as gastrointestinal tract (GIT) disorders, diabetes, infectious diseases and inflammation. AIMS: Several relevant aspects of different fractions of leaf extracts of Bauhinia bowkeri (BAB), Bauhinia galpinii (BAG), Bauhinia petersiana (BAP), and Bauhinia variegata (BAV) used in South African traditional medicine to alleviate diarrhoea related symptoms were evaluated. MATERIALS AND METHODS: The antioxidative activities of the extracts were determined using the 2, 2-diphenyl-1-picrylhydrazyl (DPPH), 2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS(+)) radical scavenging and ferric reducing antioxidant power (FRAP) methods. In vitro antimicrobial activities of the extracts were determined against bacterial strains (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Enterococcus faecalis) and clinical isolates of the opportunistic fungal strains (Aspergillus fumigatus, Candida albicans, and Cryptococcus neoformans) using a serial dilution microplate method. The polyphenolic contents were quantified using standard methods, and anti-inflammatory activities of the crude extracts were determined using the cyclooxygenase and soybean 15-lipoxygenase enzyme inhibitory assays. The safety of the extracts was evaluated by determining the cytotoxicity against Vero cell lines. RESULTS: The acidified 70% acetone crude extract and their fractions had good antiradical potency against the DPPH and ABTS radicals. The methanol soluble portions of the butanol fractions were more potent (EC(50) ranges from 0.64 ± 0.05 to 1.51 ± 0.07 and 0.88 ± 0.18 to 1.49 ± 0.09 µg/ml against DPPH and ABTS radical respectively) compared to the standard, trolox and ascorbic acid (EC(50) ranges from 1.47 ± 0.24 to 1.70 ± 0.27 µg/ml) for both DPPH and ABTS. The crude extracts contained variable quantities of phenolic content. The crude extracts and their fractions had weak to good antimicrobial activities, inhibiting the growth of the organisms at concentrations ranging from 39 to 2500 µg/ml. The BAG crude extract and its fractions were the most active against the fungi (MICs ranging from 39 to 625 µg/ml) while the BAB extract and its fractions were the least active with the MICs ranging between 39 and 2500 µg/ml. Aspergillus fumigatus was the least susceptible fungus while Cryptococcus neoformans was the most susceptible. The phenolic-rich crude extracts of BAB, BAG, and BAP had moderate to good dose-dependent cyclooxygenase-1 enzyme inhibitory activity with inhibitions between 22.8% and 71.4%. The extracts were however, inactive against cyclooxygenase-2. The extracts had some level of cytotoxicity towards Vero cell lines, reducing cell viability to less than 10% at concentrations more than 50 µg/ml. CONCLUSION: The biological activities observed in Bauhinia species provide a scientific basis for the use of the plants in traditional medicines to treat diseases with multi-factorial pathogenesis such as diarrhoea, with each aspect of activity contributing to the ultimate therapeutic benefit of the plants. However, the use of the phenolic-rich extracts of these plants to treat diarrhoea or any other ailments in traditional medicine needs to be monitored closely because of potential toxic effects and selective inhibition of COX-1 with the associated GIT injury.

In vitro screening of traditional South African malaria remedies against Trypanosoma brucei rhodesiense, Trypanosoma cruzi, Leishmania donovani, and Plasmodium falciparum.

Three hundred extracts were prepared from plants traditionally used in South Africa to treat malaria and screened in vitro for activity against Trypanosoma brucei rhodesiense, Trypanosoma cruzi, Leishmania donovani, and Plasmodium falciparum. For the 43 extracts which inhibited the growth of one or more parasites to more than 95 % at 9.7 µg/mL, the IC50 values against all four protozoal parasites and cytotoxic IC50s against rat myoblast L6 cells were determined. Amongst the most notable results are the activities of AGATHOSMA APICULATA (IC50 of 0.3 µg/mL) against Plasmodium falciparum, as well as Salvia repens and Maytenus undata against Leishmania donovani with IC50s of 5.4 µg/mL and 5.6 µg/mL, respectively. This screening is the starting point for a HPLC-based activity profiling project in antiprotozoal lead discovery.

Bufadienolides from Drimia macrocentra and Urginea riparia (Hyacinthaceae: Urgineoideae).

The bufadienolides, rubellin and riparianin were isolated from the bulbs of Drimia macrocentra and Urginea riparia (Hyacinthaceae) respectively. Rubellin and riparianin contain a carbohydrate moiety doubly linked to the bufadienolide aglycone at the C-2 and C-3 positions. Riparianin showed moderate activity when tested against MCF7 (breast), TK10 (renal) and UACC62 (melanoma) cell lines.

Eucosterol-type nortriterpenoids from Merwilla natalensis.

The bulbs of Merwilla natalensis have yielded two known homoisoflavanones, the known spirocyclic homoisoflavanone, scillascillin, four known nortriterpenoids, and the new nortriterpenoid, (22R,23S)-17alpha,23-epoxy-22,29-dihydroxy-27-nor-lanost-8-en-3,24-dione (1), bisnortriterpenoid, (22R,23S)-17alpha,23-epoxy-3beta,22,24xi-trihydroxy-27,28-bisnor-lanost-8-ene (2), and trisnortriterpenoid, (23S)-17alpha,23-epoxy-3beta,24xi-dihydroxy-27,28,29-trisnor-lanost-8-ene (3). The structures of 1-3 were determined by spectroscopic methods.