M. van de Venter

In vitro anti-HIV activity of five selected South African medicinal plant extracts

AIM OF THE STUDY Five South African medicinal plants, Bulbine alooides (L.) Willd. (Asphodelaceae), Crinummacowani Baker (Amaryllidaceae), Hypoxis sobolifera var. sobolifera (Jacq.) Nel (Hypoxidaceae), Leonotisleonurus (L.) R.Br. (Lamiaceae) and Tulbaghiaviolacea Harv (Liliaceae) used for the treatment of various ailments, including infectious diseases, were screened for activity against human immunodeficiency virus (HIV). MATERIALS AND METHODS Aqueous and ethanol extracts were tested for inhibitory activity in HIV-1 infected CEM.NK(R)-CCR5 cells, and against HIV-1 reverse transcriptase (RT) and HIV-1 protease (PR). RESULTS In CEM.NK(R)-CCR5 cells, ethanol extracts of Leonotisleonurus inhibited HIV-1 significantly (33% reduction in HIV-1 p24, P<0.05). HIV-1 RT inhibition (> or =50%) was shown for extracts of Bulbine alooides (aqueous and ethanol), Hypoxis sobolifera (aqueous and ethanol) and Leonotisleonurus (aqueous), but inhibitory activity was lost upon dereplication for removal of non-specific tannins/polysaccharides. HIV-1 PR inhibition was observed for extracts of Hypoxis sobolifera (aqueous), Bulbine alooides (aqueous and ethanol) and Leonotisleonurus (ethanol). Only ethanolic extracts of Bulbine alooides and Leonotisleonurus retained HIV-1 PR inhibition after dereplication with IC50 of 94 microg/ml and 120 microg/ml, respectively. CONCLUSION The dereplicated ethanolic extracts of Leonotisleonurus and Bulbine alooides showed the greatest anti-HIV potential in this study through inhibition of HIV-1 PR.

Hypoglycaemic activity of four plant extracts traditionally used in South Africa for diabetes

AIM To validate plant species for hypoglycaemic activity. MATERIALS AND METHODS Four plants were investigated for hypoglycaemic activity by evaluating inhibiting effects on carbohydrate-hydrolising enzymes: alpha-glucosidase and alpha-amylase. Acetone plant extracts were screened against C2C12 myocytes, 3T3-L1 preadipocytes and Chang liver cells by measuring glucose uptake. Cytotoxicity was done in preadipocytes and hepatocytes. RESULTS Extract of Euclea undulata rootbark exhibited highest activity, displaying a glucose uptake of 162.2% by Chang liver cells at 50 microg/ml. An inhibition concentration of 50% for Euclea undulata was found to be 49.95 microg/ml for alpha-glucosidase and 2.8 microg/ml for alpha-amylase. No cytotoxicity was recorded for Euclea undulata, while Schkuhria pinnata and Elaeodendron transvaalense exhibited cytotoxicity at 12.5 microg/ml. Alpha-glucosidase and alpha-amylase assays showed inhibitory activity on enzymes for three plant extracts. CONCLUSION Euclea undulata, Schkuhria pinnata and Elaeodendron transvaalense showed in vitro hypoglycaemic activity. Schkuhria pinnata and Elaeodendron transvaalense indicated cytotoxicity on 3T3-L1 preadipocytes and Chang liver cells. Euclea undulata, Pteronia divaricata and Elaeodendron transvaalense inhibited alpha-glucosidase and alpha-amylase enzymes. ETHNOPHARMACOLOGICAL RELEVANCE Screening of plant extracts scientifically validated traditional use of Euclea undulata for treatment of diabetes. Cytotoxicity results revealed that acetone extracts of Schkuhria pinnata and Elaeodendron transvaalense are toxic and raise concern for chronic use.

In vitro anti-HIV-1 properties of ethnobotanically selected South African plants used in the treatment of sexually transmitted diseases

ETHNOPHARMACOLOGICAL RELEVANCE [corrected The plants selected in this study are used traditionally in the treatment of sexually transmitted diseases and traditional healers interviewed claimed these plants can also help AIDS patients. AIM To evaluating the in vitro anti-HIV properties of selected plants in various bioassays. MATERIALS AND METHODS The extracts were evaluated for their inhibition against alpha-glycohydrolase, reverse transcriptase and viral proteins (NF-kappaB and Tat) which play a significant role in the HIV life cycle. RESULTS Terminalia sericea extract (IC(50)=92mg/ml) exhibited a considerable alpha-glucosidase inhibitory activity which was better than acarbose (IC(50)=131mg/ml) under our assay conditions. In the reverse transcriptase assay, T. sericea also showed good inhibitory activity (IC(50)=43mg/ml), which was higher than that of the reference drug, Adriamycin (IC(50)=100mg/ml). The ethyl acetate extract of Elaeodendron transvaalense exhibited the most potent inhibitory activity in both the NF-kappaB and Tat assays with inhibitory activity of 76% and 75% respectively at a concentration of 15mg/ml. The acetone and chloroform extracts of E. transvaalense and Zanthoxylum davyi also showed good activity in the NF-kappaB and Tat assays.

The biological activity of the histidine-containing diketopiperazines cyclo(His-Ala) and cyclo(His-Gly)

Two cyclic dipeptides, cyclo(His-Ala) and cyclo(His-Gly,) were synthesized from their linear counterparts and their structures elucidated using standard elucidation techniques. Molecular modeling and predictive NMR results indicated that the majority of energetically favourable conformers adopted a boat conformation with respect to the diketopiperazine ring. Cyclo(His-Ala), at concentrations of 100 microM inhibited the growth, in vitro, of various cancer cell lines, including HT-29, MCF-7 and HeLa carcinoma cells while cyclo(His-Gly) inhibited the growth of MCF-7 cells. While the antibacterial potential of these two compounds was limited, both cyclic dipeptides significantly inhibited the growth of C. albicans. Both compounds at a concentration of 100 microM resulted in a decrease in heart rate, coronary flow rate and left ventricular systolic pressure in the isolated rat heart. Inhibition of thrombin, amounting to a 63.3% and 36.7% reduction in the rate of fibrin formation, was noted for cyclo(His-Ala) and cyclo(His-Gly), respectively. While cyclo(His-Ala) showed no notable effects on platelet aggregation, cyclo(His-Gly) significantly inhibited both pathways tested with greatest effects on thrombin-induced platelet aggregation, yielding an IC(50) of 0.0662 mM (R(2)=0.989). The results of the anticancer and hematological studies indicate that histidine-containing diketopiperazines have potential as a novel group of cytotoxic agents with antithrombotic effects.

The synthesis and anticancer activity of selected diketopiperazines.

Six selected diketopiperazines, cyclo(Gly-Val), cyclo(Gly-D-Val), cyclo(Gly-Leu), cyclo(Gly-Ile), cyclo(Phe-Cys) and cyclo(Tyr-Cys), were synthesized via various synthetic routes. Their potential to inhibit cancer cell growth in HT-29, HeLa and MCF-7 cells was determined. Cyclo(Tyr-Cys) caused the greatest inhibition in cervical carcinoma cells with near equivalent activity against HT-29 and MCF-7 cells. The other cyclic dipeptides tested were effective in the inhibition of colon, cervical and breast carcinoma cells, respectively, but the percentage inhibition was lower than for cyclo(Tyr-Cys).

Anticancer Activity of Steroid Alkaloids Isolated from Solanum aculeastrum.

Abstract Solanum aculeastrum. Dunal is a medicinal plant that has long been used to treat various cancers and many other conditions in the Eastern Cape Province of South Africa. In this study, two steroid glycosides were isolated from the berries of this plant, which were identified as tomatidine and solasodine by spectroscopic techniques. Effects on cell growth of these compounds were investigated with HeLa, MCF7, and HT29 cancer cell lines. The IC50 values confirmed that tomatidine and solasodine had the highest inhibitory effect on HeLa cells and the IC50 of the combined compounds was lower than the value for solasodine and unchanged from that of tomatidine. However, the IC50 values of the two compounds combined was also lower in HT29 and MCF7 cells than for the individual compounds. Both tomatidine and solasodine inhibited cell growth by blocking the cell cycle in the G0/G1 phase after 24-h exposure with an increase from 55.6% to 64.2% and 66.8%, respectively. Using annexin V–FITC/PI staining by flow cytometry, the compounds showed very low apoptotic indices.

Hypoglycemic evaluation of a new triterpene and other compounds isolated from Euclea undulata Thunb. var. myrtina (Ebenaceae) root bark

AIM OF THE STUDY Investigate the hypoglycaemic activity of the four isolated compounds from a crude acetone extract of the root bark of Euclea undulata var. myrtina, which is used by traditional healers in the Venda area, Limpopo Province in the treatment of diabetes. MATERIAL AND METHODS The hypoglycaemic activity of the four compounds isolated from Euclea undulata was determined by in vitro screening of glucose utilization by C2C12 myocytes at a concentration of 25 μg/ml or 50 μg/ml. The inhibition of α-glucosidase was also tested at concentrations ranging from 0.02 to 200.00 μg/ml. RESULTS Assay-guided isolation of the crude acetone extract of the root bark of Euclea undulata var. myrtina afforded a new triterpene, α-amyrin-3O-β-(5-hydroxy) ferulic acid (1), in addition to three known compounds; betulin (2), lupeol (3) and epicatechin (4). The in vitro results on C2C12 myocytes suggest that compound 4 may have some effect to lowers blood glucose levels, whereas compound 1 has the ability to inhibit α-glucosidase at a concentration of 200.0 μg/ml with an IC₅₀ value of 4.79 that correlates with that of the positive control acarbose IC₅₀ value 4.75. CONCLUSION The results suggest that 4 may have some ability to lower blood glucose levels, whereas 1 has the ability to inhibit α-glucosidase. ETHNOPHARMACOLOGICAL RELEVANCE These findings corroborate the ethnomedicinal use of Euclea undulata by traditional healers for the treatment of diabetes as two substances was isolated from the acetone plant extract that exhibit hypoglycaemic activity.

Plant species used in the treatment of diabetes by South African traditional healers: an inventory.

The indigenous people of southern Africa have a long history of traditional plant usage for medicinal purposes, with about 4,000 taxa being so employed. Traditional medicines continue to play a significant role in the treatment of life-threatening diseases such as malaria, tuberculosis, diabetes and AIDS in the developing world, although no adequate scientific evidence has been documented in support of their healing properties. The primary goal of this paper is to summarize information on some of the plant species used by traditional healers for the treatment of diabetes in South Africa. The information obtained is from published literature as well as personal communication with various traditional healers and herbalists from different areas. In total, the information of 32 plant species, representing 20 families, traditionally used by healers in the treatment of diabetes, has been discussed, of which 14 are currently being investigated for their hypoglycemic activity by various scientists at the University of Pretoria.

Influence of pre-treatment on yield chemical and antioxidant properties of a Nigerian okra seed (Abelmoschus esculentus moench) flour

Okra seeds are reported to be limited to re-generational purpose in Nigeria while majority are discarded as unfit for this purpose. Studies were carried out to evaluate the effect of soaking and blanching on the yield, proximate composition and antioxidant activity of okra seed flour. Pre-treatment by soaking and blanching were found to increase yield which was time dependent. The range mean obtained for protein, fat, ash and fiber contents were 46.10-38.99, 28.08-25.08, 3.95-3.15 and 3.76-3.10, respectively. Slight but significant DPPH radical scavenging activity increase was observed in soaked samples at 18th-h while blanching resulted into progressive decrease.

Production of polysaccharide and surfactin by Bacillus subtilis ATCC 6633 using rehydrated whey powder as the fermentation medium

The aim of this research was to assess the amounts of polysaccharide and surfactin produced by Bacillus subtilis ATCC 6633 in rehydrated whey powder (RWP) as the growth medium. One-day-old cultures of B. subtilis (∼4.6 log cfu/mL) were inoculated into 100mL of 10, 15, or 20% (wt/vol) RWP and incubated at 30°C for 72 h. To analyze the effects of lactose and protein on polysaccharide and surfactin production, 6 RWP solutions containing different levels of lactose and protein were also used as media. The number of vegetative cells and spores, pH, viscosity, and the concentration of lactose were determined at 0, 24, 48, or 72 h of fermentation. The levels of polysaccharide and surfactin produced after 72 h of fermentation were measured using HPLC and the phenol-sulfuric acid method, respectively. During 72 h of fermentation, B. subtilis populations increased from 4.6 to 10.54, 9.82, and 9.67 log(10) cfu/mL in 10, 15, and 20% RWP, respectively. The number of B. subtilis spores in 10% RWP increased from 3.91 to 4.72 log(10) cfu/mL after 48 and 72 h of fermentation, respectively. The increased level of lactose or protein in RWP did not significantly change the vegetative growth. After 72h of fermentation, the pH of RWP decreased from 5.70 to 4.99 with a slight increase in viscosity. Polysaccharide levels in 10, 15, and 20% RWP after fermentation were 513.6, 613.5, and 768.3mg/L, respectively, with B. subtilis producing 0.18 to 0.29 g/L of surfactin after 72 h of fermentation. The polysaccharide or surfactin production was not changed significantly by addition of protein or lactose to RWP. These results indicate that RWP is a good fermentation substrate for surfactin and polysaccharide production.