Evaluation of phytochemical, antioxidant and antimicrobial properties ofdifferent accessions of Persicaria minor (kesum)

Persicaria minor (Huds.) Opiz. or locally known as kesum is an aromatic medicinal plant from the family Polygonaceae. It is originated from Southeast Asian countries such as Indonesia, Vietnam, Thailand and Malaysia. The plant leaf has many claims with regards to its traditional uses, but is popularly consumed as fresh vegetable (ulam), flavouring agent and food additive. Previous research showed that P. minor possessed antioxidant and antimicrobial activities. However, information on the effect of antioxidant and antimicrobial activities of different accessions of P. minor is still lacking. Therefore, the current work was undertaken to evaluate six different accessions of P. minor comprising MKSM002, MKSM004, MKSM006, MKSM011, MKSM013 and MKSM020. These accessions were obtained from various locations in Peninsular Malaysia and established in MARDI Headquarters herbal germplasm. The aerial parts of the plants were dried under a hot air oven at 50°C prior to extraction. From the results, MKSM002 and MKSM006 methanolic extracts were the most potent antioxidant due to the strongest ferric reducing (13.19 µmol Fe/g) and DPPH radical scavenging (IC50 0.39 mg/mL) activities, respectively. Antimicrobial activity was determined against common pathogenic bacteria i.e., Bacillus cereus, Staphylococcus aureus, Cronobacter sakazakii and Enterobacter aerogenes using disc diffusion assay. Among the extracts, MKSM002, MKSM004 and MKSM006 were the most effective, being able to significantly (P<0.05) inhibit the growth of most of the bacteria tested. The most active inhibition was recorded against E. aerogenes with the diameter of inhibition zones ranging from 14.12 mm to 15.75 mm. Phytochemical screening of the extracts showed that these extracts contained a substantial amount of total phenolics and total flavonoids. Liquid chromatography-tandem mass spectrometry-quadrupole time-of-flight (LC–MS-QTOF) analysis of the selected extracts revealed the presence of various phytochemicals, with flavonoids and their derivatives being the most predominant ones. In conclusion, the selected P. minor accessions can be promoted as a source of planting material source for breeding, conservation and commercial purposes. The findings are also important in the search for antioxidant supplementation and healthcare products in the future.