In vitro Assessment of Phytoconstituents, Efficacy and Cytotoxicity of Extracts from Medicinal Plants on Prostate Cancer C4-2 Cells
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Phenolic compounds are products of secondary plant metabolism known for their biological activity including their antimicrobial, antioxidant, analgesic, stimulant, anti-carcinogenic, and aphrodisiac properties. The main objective of this study was to assess the content and properties of bioactive phytochemicals in the extracts of Prunus africana, Pausinystalia yohimbe, Moringa oleifera, Momordica charantia and Orthero spp and determine their potency/cytotoxic effects. Total phenolics (TPC), carotenoids, anthocyanins, and flavonoids and their antioxidant properties in water, ethanol, methanol, acetone, and dichloromethane extracts of the different plant parts of these five plants were measured using the Folin-Ciocalteu, 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (DPPH), ferric reducing antioxidant power (FRAP), and 2,2′-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) radical scavenging (ABTS) assays. For most of the plant samples, extraction yields were highest in ethanol or methanol extraction solvents. The highest total phenolic content (1397.33 mg GAE/g) was seen in the methanol extract of P. africana bark from Cameroon, while the acetone extract of M. charantia leaves yielded the highest total flavonoid content (217.33 mg RU/g). The FRAP values in this study ranged from 7.09 in the DCM extract of P. africana bark (Kenya) to 131.57 mM Fe2+/g in ACE extract of M. charantia leaf. The EC50 values for the acetone and methanol extracts of P. africana bark (Cameroon), methanol and ethanol extracts of P. yohimbe leaf and the methanol extract of P. yohimbe root were comparable to ascorbic acid (0.18 mg/mL). TPC showed a strong positive correlation with TFC of acetone extracts of P. yohimbe and Orthero roots, FRAP of ethanol and methanol extracts of P. africana (Cameroon) root, acetone and methanol extracts of P. africana (Cameroon) leaf, methanol extracts of P. yohimbe leaf, M. charantia leaf and the TEAC of P. africana (Cameroon) bark water extract, ethanol extracts of P. yohimbe leaf and Orthero root. Using high performance liquid chromatography (HPLC), seven phenolic acids, namely methyl 4-hydroxybenzoate, protocatechuic acid ethyl ester, trans-sinapic acid, vanillic acid, trans-ferulic acid, p-coumaric acid and caffeic acid were isolated from nine extracts of P. africana and P. yohimbe. The most abundant phenolic acids were vanillic acid (116.41 mg/g dry extract in methanol extract of P. yohimbe leaf) and trans-sinapic acid (102.22 mg/g dry extract in water extract of P. africana bark). On gas chromatographic phytosterol analysis, stigmasterol, β-sitosterol and campesterol were present in all plant parts of P. africana and P. yohimbe except for P. africana root and bark, where campesterol was not detected. β-sitosterol showed the highest concentration and variation between plant parts, ranging from 0.55-2.26 in the bark and leaf and 0.35-0.46 mg/g in the root and leaf of P. africana and P. yohimbe, respectively. Using different concentrations of P. africana extracts, prostate cancer C4-2 cells, a hormonally insensitive subline of LNCaP cells, were treated in a proliferation assay. A concentration dependent inhibition of cell growth in cells treated with P. africana bark and root extracts was present from days 1 through 3 of incubation, with the methanol extract of the bark showing the strongest effect. Compared to other plant parts, leaf extracts were significantly less cytotoxic at the same concentrations. All plant part extracts contained significant amounts of phenolic compounds and pigments with potent antioxidant activity comparable to that of ascorbic acid, in the case of P. africana, demonstrated in vitro cytotoxicity.