Bioactive Phenolic Compounds From Plants Traditionally Used To Treat Microbial Skin Infections
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Date
2016-09
Authors
Hashim, Nurul Shafiqah
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Abstract
This study was initially aimed to verify the therapeutic values of plants that are traditionally used to treat microbial skin infections. Based on hypothesis that the extracts should have antimicrobial and antioxidant activities in order to accelerate the healing of skin, a total of 120 phenolic extracts were screened for both activities. The antimicrobial activities were determined against nine skin pathogenic microorganisms. The leaf extracts of Anacardium occidentale, Cassia alata and Terminalia catappa were found to possess a broad spectrum of antimicrobial activities. The primary antioxidant potentials were determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) free radical scavenging, and ferric reducing antioxidant potential (FRAP) assays, and metal chelating assay was used to measure the secondary antioxidant activity. The extract of T. catappa showed higher activities in all assays. Six leaf extracts that have higher rank for both activities (from Macaranga triloba, Punica granatum, Rosa chinensis, Rhodomyrtus tomentosa, Syzygium jambos and T. catappa) showed moderate anti-inflammatory activities when determined using cyclooxygenase and 5-lipoxygenase inhibitory assays. Many earlier studies reported higher activities of hydrolyzed extracts than crude extracts, hence the six extracts were hydrolyzed for further assessments. The hydrolyzed extract of R. tomentosa was found to have the highest antimicrobial activity against Corynebacterium minutissimum ATCC 23348, Micrococcus luteus ATCC 4698, Staphylococcus aureus ATCC 12600 and Candida albicans ATCC 10231 with minimum inhibition
concentration (MIC) of 15.63 μg/mL. The highest primary antioxidant activity was shown by the hydrolyzed extract of P. granatum, while the crude extract of T. catappa gave the highest secondary antioxidant activity. The crude and hydrolyzed extracts of A. occidentale and C. longa were found to give higher activities compared to other extracts with MIC values ranging between 125 μg/mL and 1000 μg/mL against Pseudomonas aeruginosa (ATCC 27853, ATCC 15442 and ATCC 9027). Phenolic compounds in 12 hydrolyzed extracts were detected using Ultra Performance Liquid Chromatography (UPLC) with diode array detector and were confirmed using Liquid Chromatography-Mass Spectrometry (LC-MS). Among four phenolic compounds (myricetin, quercetin, kaempferol and gallic acid) that were commonly identified from the hydrolyzed extracts and their glycosides (myricetin-3-O-rhamnoside, quercetin-3-O-rhamnoside, quercetin-3-O-glucoside and kaempferol-3-O-glucoside), myricetin showed the highest activity against all the tested bacteria and C. albicans with MIC values ranging between 7.81 μg/mL and 62.5 μg/mL. P. aeruginosa was also susceptible to myricetin with MIC value of 31.25 μg/mL. Thus, myricetin was identified to be the bioactive phenolic compound in the extracts.
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Verify the therapeutic values of plants that are traditionally used , to treat microbial skin infections.