To evaluate antimicrobial activity and isolate chemical compounds from Piper betle L for fighting with bacterial foodborne diseases and food poisoning.

The antimicrobial activity of four solvent extracts (methanol, ethanol, aceton and ethyl acetate) of Piper belte L against nine microbes (S. aureus, L. monocytogenes, E. faecalis, E. coli, P. aeruginosa, K. pneumoniae, S. enterica serovar Typhimurium, S. flexneri and C. Abricans) was evaluated, in which the highest antimicrobial activity was on E. coli, S. aureus, E. fecalis and C. Abricans (inhibition zones of 15 – 27 mm);
The minimum inhibitory concentrations (MIC) of solvent extracts of P. belte were determined for the nine microbes tested (MICs = 40 – 100 mg/ml), in which the methanol extract showed highest antimicrobial activity towards E. coli, S. aureus and C. albicans (MIC = 40 mg/ml). These results suggest that the P. belte extracts possesed board antimicrobial activity and effectively against Gram + bac;  
10 chemical compounds were isolated and their structures were eluciated, among them, piperbetamide A, piperbetamide B, piperbetamide C and piperbetamide D were reported for the first time, along with the six known compounds including 3,4-dihydroxyallylbenzene, 3-O-β-D-glucopyranosyl-4-hydroxyallylbenzene, 3-O-β-D-glucopyranosyl-4-methoxyallylbenzene, 4-O-β-D-glucopyranosyl-3-hydroxyallylbenzene; 4-O-β-D-glucopyranosyl-3-methoxyallylbenzene and 3,4-di-O-β-D-glucopyranosylallylbenzene.
All the 10 purified compounds had board antimicrobial activity and effectively against multidrug-resistant bacteria, with the MIC ranged from 16 to 256 µg/ml. Notably, 3,4-di-O-β-D-glucopyranosylallylbenzene exhibited strong antimicrobial activity towards on  L. monocytogenes,   methicilin-resistant S. aureus and vancomycin-resistant E. faecalis with the MIC of 16 µg/ml. Compounds  piperbetamide C and piperbetamide D had the strongest activity against only methicilin-resistant S. aureus (MIC = 16 µg/ml). Piperbetamide A, piperbetamide C, piperbetamide D, 3-O-β-D-glucopyranosyl-4-hydroxyallylbenzene and 3,4-di-O-β-D-glucopyranosylallylbenzene showed moderate antimicrobial activity against S. flexneri (MIC = 32 µg/ml).

Four new compounds including piperbetamide A, piperbetamide B, piperbetamide C and piperbetamide D were isolated for the first time from P. Belte of Vietnam. 

- Scientific papers in referred journals (list): 
Hang, L. T. T., Huy, N. Q., Tam, T. T. T., Huong, L. T., Nam, P. H., Dang, N. H., Quyet-Tien, P., Trang, D. T., Yang, S. Y. Tai, B. H. (2022). Four new N-phenethylbenzamide derivatives from the stems of piper betle and their antimicrobial activity. Nat Prod Res. Pages 1 – 9. DOI: 10.1080/14786419.2022.2114473.