Antimicrobial, cytotoxic and prelimenary phytochemical analysis of four medicinal plants and their formulation

Abstract

BACKGROUND: Medicinal plants form an important part of the Southern African cultural heritage. Indigenous populations, for example the Vha-Venda people, tend to use medicinal plants in formulations rather than western medicines for health and survival. In order to certify and give scientific credibility to the use of medicinal plants formulations used by Vha-Venda people for the treatment of diseases, several assays were carried out. The present study was aimed at assessing phytochemical content, antimicrobial, antioxidant and cytotoxic activities of four indigenous Venda medicinal plants in a formulation and compare their activity with each plant used individually. METHODS: Peltophorum africanum (roots), Pterocarpus angolensis (bark), Terminalia sericea (roots) and Ximenia caffra (roots) were collected from the Thohoyandou area. The collected plant parts were extracted with methanol and water respectively. Individual plant extracts and Five designed formulations were tested for their antimicrobial activity against Staphylococcus aureus ATCC 25923 (Methicillin Resistant), Staphylococcus aureus ATCC 33591(Methicillin Susceptible), beta lactamase producing Klebsiella pneumonia (ATCC 700603) and extended spectrum beta lactamase producing E. coli (ATCC 35218), four clinical isolates of Candida spp and Cryptococcus neoformans using the Broth dilution method. Minimum bactericidal concentration (MBC) of the extracts was determined by culturing the contents of minimum inhibitory concentration (MIC) on nutrient agar. Similarly, minimum fungicidal concentration (MFC) was also determined by culturing contents of MIC in sabouraud dextrose agar (SDA). Extracts were further assessed for their total phenolic content, total flavonoid content and Qualitative phytochemical analysis. The antioxidant ability of the plants extracts and formulations to scavenge free radical DPPH was also determined. The plant formulations were assessed for their anti-HIV activity using the reverse transcriptase

colorimetric assay kit. Cytotoxicity against human lymphatic endothelial cells (HLEC) was determined using MTT assay. RESULTS: Methanolic and aqueous extracts of T. sericea exhibited the best antifungal and antibacterial activities whilst P. angolensis and X. caffra showed poor activities. Methanolic plant formulations showed good activities compared to aqueous formulations. However, Fractional Inhibition Concentration Index showed that there was 1 synergistic interaction, 25 additive interactions and 14 antagonistic interactions between the plant extracts. The methanolic formulation 3 showed the best overall phenolic content at 11.85±0.109 mgGAE/g whilst aqueous X. caffra extract showed the least content at 4.546±0.104 mgGAE/g. Higher total flavonoid contents were seen in methanolic formulation 4 at 2.75±0.02 mgQE/g. Qualitative phytochemical analysis revealed the presence of flavonoids, phenolics, terpenoids, tannins, saponins and steroids in 80% of the tested plant extracts and formulations. All plant extracts and formulations exhibited good antioxidant activity against DPPH. The methanolic formulation showed the best antioxidant activity with IC50 of 0.094 ± 0.33μg/ml. For anti- HIV inhibition, all formulations at 200μg/ml exhibited higher percentage of HIV-1 reverse transcriptase inhibition with methanolic mixture 3 being the best overall at 97.5% activity whilst aqueous mixture5 was the least active with 63.03% inhibition activity. Moreover, the best anti-HIV activity at 100μg/ml was exhibited by methanolic mixture 3 at 71% inhibition. Furthermore, aqueous X. caffra, mixture 2 inhibited 26% and 51% at 12.5mg/ml and 3.125mg/ml respectively. Peltophorum africanum and mixture 5 inhibited 34%, 54% and 43% at 3.125mg/ml, 6.25mg/ml and 12.5 mg/ml respectively of Human Lymphatic Endothelial cells growth. CONCLUSIONS: The results from the study indicated that most of the commonly used traditional medicinal Plants in the Venda region when mixed together have merit for use in traditional medical practice as they have shown good antimicrobial activities, good antioxidant xviii activities, good phytochemical activities and good cell proliferation activity. However some formulations showed antagonistic interaction against bacteria. Some Individual medicinal plants showed toxicity at higher concentrations against immune cells. Whereas formulations promoted cell proliferation, therefore, the use of such individual plants in the treatment of infections should be highly monitored as they may pose a health threat to normal immune cells. Generally, plants are potential pharmacological agents which needs to be preserved and harvested with care.