This study aimed to examine students' understanding of the antimicrobial properties of marang seed oil. Study 1 extracted marang seed oil at two fractions. InFraction 1, the marang seed oil was extracted at a pressure of 100atm, and Fraction 2 at a pressure of 300atm at constant temperature of 40⁰C and were tested for their antimicrobial properties. Results indicated that extracts of marang seed oil have a great potential as antimicrobial compounds against microorganisms: Staphylococcus aureus, Bacillus subtilis, Candida albicans, and Saccharomyces cerevisciae. In Study 2, 30 high school students studied the antimicrobial properties of marang seed oil through participatory learning. Their learning outcomes, measured in terms of their opinions on the appropriateness of throwing marang seeds, explanations on the uses of marang seeds, and suggestions on what to do wiith marang seeds, were compared to a group who studied the same topic through a teacher-centered instruction. With the experimental group scoring higher than the control group, results showed highly significant difference of the students' incremental scores in the three assessment items. Interviews with the students showed that participatory antimicrobial assay made learning of the antimicrobial properties of marang seed oil interesting, made the lesson practical rather than theoretical, promoted students' cooperation and created students' interest even after the class. Overall results indicated that the participatory learning led students to detect the inappropriateness of throwing marang seeds, their medicinal values and think of ways to harness the potentials of this untapped resource.