Biological Activity of Combretum erythrophyllum: Antioxidant, Apoptotic, and Cytotoxic Activity of the Leaf and Stembark Extract

Abstract

Species of Combretum are highly valued in Africa due to the plethora of traditional medicinal uses they may offer and the medicinally important phytometabolites they are known to contain. Traditionally, C. erythrophyllum is used to treat bacterial infections, venereal diseases, abdominal pain, sores, infertility, and labour pains, while displaying, anti-viral, anti-parasitic, cytotoxic, and mutagenic activities. There are numerous published works available on the bioactivity of phytometabolites of the leaf extracts of C. erythrophyllum; however there have been limited or no studies published on the bioactivity of the stembark. Hence, this study aimed to provide a comparative analysis of the biological activity of the leaf and stembark extracts of C. erythrophyllum. The following characters were evaluated through the emanating study: total flavonoid and phenolic content, as well as the antioxidant, cytotoxic, and apoptosis activities of the leaf and stembark extract. Methanolic extracts appeared to have the highest possible antioxidant potential among all of the tested extracts and displayed the lowest IC50 values (leaf 5.29 and stembark 4.29 µg/mL) when evaluated using the DPPH assay, the methanolic extracts appeared to quantify the largest amount of compositional phenolic content (1341.05 ± 4.4 mg/GAE/g). Methanolic extracts were the best performing, with the overall lowest IC50 values when tested against HeLa and HEK293 cells (leaf 54.53 µg/mL and stembark 18.30 µg/mL). A positive correlation between % inhibition and extract concentrations was noted for all of the assays. The extent/level of antioxidant activity was seen to be directly proportional to the flavonoid and phenolic content. Extracts with the highest total phenolic content appeared to display the strongest cytotoxic activity. This study integrated the use of fluorescence microscopy with acridine orange staining in order to accurately determine the viability of cells. A direct correlation was observed between the results obtained from the cytotoxicity and apoptosis assay. It may be concluded that the antioxidant properties, total phenolic, and total flavonoid content were directly proportional to the apoptotic and cytotoxic activity expressed by the tested extracts. Focus should now be placed on isolating phytocompounds of importance from the best performing extracts. The transformation of an isolate into a drug of pharmacological importance has yet to be appraised on a large scale. Therefore, further evaluation of this species and particularly the transformation of the isolates needs to be explored as this species has shown immense medicinal potential.