Ronny Horax,1,2 Navam Hettiarachchy,1 Pengyin Chen,3 Shahidul Islam,4
and Michael Johnson1
1Department of Food Science, University of Arkansas, Fayetteville, AR 72704, U.S.A.
2Department of Pharmacy, Health Polytechnic, Makassar, Sul-sel 90223, Indonesia
3Department of Crop, Soil, and Environmental Sciences, University of Arkansas,
Fayetteville, AR 72701, U.S.A.
4Department of Agriculture, University of Arkansas at Pine Bluff, AR 71601, U.S.A.
BACKGROUND : Bitter melon (Momordica charantia L.), a member of cucurbitaceae, is cultivated for its edible fruit as a vegetable and for medicinal purposes. Phenolic compounds from fruits and vegetables have been intensively studied due to their potency to prevent oxidative damages by quenching free radicals as well as inhibit microbial growth. Due to consumer preferences on natural products over synthetic substances, there is an increase demand for the use of plant phenolic extracts for minimizing oxidation in food products or combating diseases.
OBJECTIVE -Our study aimed to determine phenolic contents in bitter melon fruit tissues, extract the phenolics using aqueous ethanolic solvents, and evaluate the obtained phenolic extracts for their antioxidant and antimicrobial activities.
RESULTS-The phenolic contents of separated bitter melon tissues (pericarp/fleshy portion, rind/seed coat tissue, and seed) from various varieties ranged from 4.64 to 8.94 mg chlorogenic acid equivalent (CAE)/g (dry weight basis) with the main phenolic compounds were gallic acid, gentisic acid, catechin, chlorogenic acid, and epicatechin. Total phenolic assessment demonstrated 80% of ethanol to be the optimal solvent to extract phenolics either from pericarp or seed of the mature bitter melon fruits. Similar to the total phenolic contents, there were significant effects of the ethanol levels as the extraction solvents on their antiradical extract power values (P < 0.05) that ranged from 40 to 81 mg DPPH (2,2-diphenyl-1-picrylhydrazyl)/g extract; 80% ethanol extract showed the most effective antiradical power. The extracts were more effective as antimicrobial agents specifically against infectious foodborne pathogenic Gram positive bacteria such as L. monocytogenes (> 4 log CFU/mL reduction) and nominally effective in inhibiting Gram negative bacteria such as E.coli and S. Typhimurium (<3 log CFU/mL reduction).
CONCLUSION -The phenolic extracts from bitter melon fruit flesh were more effective than those from bitter melon fruit seeds. These natural plant phenolic extracts can be a potential antioxidant and antimicrobial agent for application in food system. The phenolic compounds with antioxidant activities in bitter melon extracts could also have a potency as natural immunomodulators for curing infectious diseases. These extracts could be used alone or concomitantly with antibiotics to fight future infectious diseases through their potential immunomodulatory activity by either preventing phagocytosis caused by leukocyte migration as a normal immune response to infections, regulating macrophage and lymphocyte activations, or minimizing oxidative stresses that can cause autoimmune disorders resulting higher susceptibility to infections.