Estimation of Total Phenolic and Flavanoid Contents in Leaf Extracts of Selected Kenyan Anti-obesity Medicinal Plants and Their Antioxidant Activities

Author: Evans Omwango, Prof. Justus Onguso, Prof. John Onchora and Dr. Peter Kirira

ABSTRACT

Dissatisfaction with the high costs and hazardous side effects of the anti-obesity drugs currently available in the market, the potential of natural products for obesity treatment is under exploration. The study sought to screen selected medicinal plants, Mangifera indica, Psidium guajava, Syzygium cumini and Persea americana, used in the treatment of obesity by herbalists in Kenya for their phenolic and flavonoid contents and antioxidant activity. Methanol extracts of leaf samples of four anti-obesity medicinal plants, collected from different agro-climatic regions in Kenya, were prepared. The total phenolic contents were measured spectrophotometrically by Folin-Ciocalteau method and total flavaonoid contents by the aluminum chloride colorimetric method. Free radical scavenging activity was evaluated using 2,2-diphenyl-1-picryl-hydrazyl (DPPH) assay. The highest amounts of phenolics were recorded in P. guajava extracts from the coast region (104.35 ± 23.64 mg GAE/g extract) and the lowest amount in P. americana extracts from the central region (40.15 ± 14.07 mg GAE/g extract). The highest amounts of flavonoids were recorded in S. cumini extracts from the coast region (67.83 ± 9.98 mg quercetin/g extract) and the lowest amount in P. americana extracts from the western region (38 ± 10.45 mg quercetin/g extract). The highest IC50 values in the DPPH scavenging assay were recorded in P. guajava extracts from the coast region (41.2 µ/ml). A significant linear correlation was observed between the antioxidant power and phenolic contents (R2 = 0.97). The study findings show that polyphenolic compounds in the extracts are responsible for the free radical scavenging capacity of the plants.

Citation

Omwango, E., Onguso, J., Onchora, J., and Kirira, P. (2022). Estimation of Total Phenolic and Flavanoid Contents in Leaf Extracts of Selected Kenyan Anti-obesity Medicinal Plants and Their Antioxidant Activities. Journal of Contemporary Biotechnology, Volume 3, Issue 2, P 12 ‐ 13, 2022.