IN VITRO EVALUATION OF THE BIOACTIVITY OF GNIDIA POLYCEPHALA AND SENECIO SERRATULOIDES

Abstract

The worldwide increase in disability and death rates due to non-communicable and infectious diseases may partly be attributed to the expense, inaccessibility and severe side effects of current treatment strategies. Medicinal plants provide an avenue to discover and develop cheap, safe yet potent alternative therapies that are easily accessible and culturally acceptable. This study evaluated the bioactivity of extracts from Gnidia polycephala and Senecio serratuloides in order to assess their potential for drug development. The acetone, methanol and aqueous plant extracts were tested for anticancer activity as well as for cytotoxicity in vitro using the Sulforhodamine B assay. The α-amylase and α-glucosidase inhibition assays were used to evaluate their potential as hypoglycemic agents. The antimicrobial efficacy of the plant extracts against specific bacteria was determined by means of the broth microdilution method. The phytochemical constituents of the plant extracts were detected using standard qualitative phytochemical screening techniques as well as Gas chromatography. The extracts from Gnidia polycephala and Senecio serratuloides had weak (IC50) or no anticancer activity against renal, melanoma and breast cancer cell lines. The extracts were also classified as low or weak hazard against the normal human fetal lung fibroblast cell line and were selective for the cancer cells and could therefore be safe to use. The acetone extract from G. polycephala showed good α-amylase inhibition at 66.34 ± 0.84%; while G. polycephala acetone (81.75 ± 0.86%), aqueous (54.84 ± 0.65%) and methanol (45.43 ± 0.56%) extracts and S. serratuloides acetone (78.86 ± 1.10%) extract showed good anti-α-glucosidase activity. Only S. aureus was susceptible to G. polycephala acetone and methanol extracts at 10 mg/ml and susceptible to S. serratuloides acetone and methanol extracts at 5 mg/ml. Hydrolysable tannins were detected in extracts from both plants, while flavonoids were detected in S. serratuloides extracts. Few medically important compounds such as 4-((1E)-3-Hydroxy-1-propenyl)-2-methoxyphenol and 2-Methoxy-4-vinylphenol were identified using Gas chromatography/mass spectrometry (GCMS). The G. polycephala extracts showed higher α-amylase and α-glucosidase enzymes inhibitory activities than the extracts from S. serratuloides and further fractionation of these extracts to determine which compounds are responsible for the α-amylase and α-glucosidase inhibition as well as to determine if the inhibition is as a result of the compounds acting synergistically or individually is recommended.