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Evaluation of Phytochemical Composition in Selected Medicinal Plants and Potential Application as Antimicrobial Agent

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dc.contributor.author Smith, Jallah Chuku
dc.date.accessioned 2020-01-17T15:01:18Z
dc.date.available 2020-01-17T15:01:18Z
dc.identifier.uri http://hdl.handle.net/20.500.12090/524
dc.description.abstract Four medicinal plants native to Cameroon (C) and Kenya (K): Prunus africana (C) bark and root, P. africana (K) bark, Pausinystalia yohimbe bark, and Orthero root were screened to assess their phytochemical compositions and antioxidant activities. The plant parts were extracted using aqueous (80%) acetone, methanol, and ethanol (solvent: water, 80:20 v/v). The antioxidant capacity of the extracts was evaluated by their ability to scavenge free radicals using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and their antiradical power (ARP); trolox equivalent antioxidant capacity (TEAC) by utilizing 2,2′-azinobis-(3-ethylbenzothiaziline-6-sulfonate) (ABTS); and ferric reducing antioxidant power (FRAP). The total phenolic content (TPC) and total flavonoid content (TFC) were estimated by the Folin-Ciocalteu (FC) and aluminum-chloride (AlCl3) assays, respectively. Pigment content was determined spectrophotometrically, and phenolic acids were quantified by high performance liquid chromatography-photodiode array detector (HPLC-PAD) using eight aqueous solvent extracts with EC50 values (±0.125), in comparison with the standard (i.e., ascorbic acid). In addition, the antimicrobial activity was demonstrated using the agar disc diffusion assay followed by the measurement of the average zone of inhibition (ZOI) in which the first five aqueous solvent extracts in the order of decreasing antioxidant power were tested against two clinical foodborne bacteria (gram-negative E. coli and gram-positive S. aureus). The highest DPPH radical scavenging activity was found in P. africana (K) bark (95.77%; aqueous acetonic extract) though its aqueous methanolic extract exhibited the lowest antioxidant power with the highest effective concentration (EC50) and lowest ARP (7.298 mg/mL and 0.137), respectively; and its aqueous acetonic extracts also exhibited the lowest TPC and TFC, respectively (166.27 mg GAE/g and 9.60 mg RU/g). However, the highest EC50 and ARP (0.093 mg/mL and 10.753 respecively), and highest TPC (1131.70 mg GAE/g) were exhibited by the aqueous ethanolic extract of P. africana (C) bark while the highest ferric reducing capacity (11.33 mM Fe2+/g) and ABTS•+ radical scavenging activity (126.87 mM TE/g) was exhibited by the aqueous acetonic and aqueous methanolic extracts of P. yohimbe bark, respectively. Moreover, the highest TFC (61.33 mg RU/g) was also exhibited by the aqueous acetonic extract of P. yohimbe bark. Except for xanthophylls, the highest recorded pigment (61.92 mg/g) in this study was exhibited by the aqueous acetonic extract of Orthero root; the highest measure of all other pigments (chlorophyll a and b; total chlorophyll, lycopene, β-carotene, carotenoids, and anthocyanin) were exhibited by the aqueous acetonic extracts of P. yohimbe bark (9.16 and 22.46; 32.21, 2.78, 6.83, 20.08, and 0.53 mg/g, respectively). There was a significant positive correlation between TPC, TFC and DPPH, and a significant negative correlation between TPC and the other two antioxidant assays (FRAP and TEAC). Methyl 4-hydrocybenzoate and protocatechuic acid were detected and quantified in all the selected extracts, trans-sinapic acid (SIA) in P. africana (C) bark and root, and ferulic acid (FA) in P. africana root extract only. P. africana (C) bark and root extracts had the highest phenolic acid in all plant parts (i.e., SIA) with recorded values >100 mg/g which agrees with their spectrophotometrically determined high TPC. All aqueous solvent controls used for extraction, inhibited the growth of both E. coli and S. aureus while the sterile blank disc controls showed no inhibitory zone. Of all the tested extracts, both concentrations (50 and 100 mg/mL) of aqueous acetonic extracts of P. africana (C) bark exhibited no growth inhibiton against E. coli but an active to highly active inhibitory zone against S. aureus (8.0 to 17.33 mm). The highest growth inhibition was exhibited by the aqueous ethanolic extract of P. africana (C) bark against S. aureus (17.33 mm). These results clearly support the potential uses of these plant parts in a wide range of applications such as antimicrobials and antioxidants.
dc.title Evaluation of Phytochemical Composition in Selected Medicinal Plants and Potential Application as Antimicrobial Agent
dc.date.updated 2019-09-05T22:09:04Z
dc.language.rfc3066 en


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