The Antibacterial Effect of Secondary Compounds in Plants

The concerns about disease-causing bacteria that can live on skin, reside on food, and invade the body are ever increasing. The common and immediate reaction to these ’germs’ is to increase the dose of antibiotics and other drugs. However, as more cases of multidrug-resistant bacteria are occurring, the search for new compounds that can target these pathogens becomes more urgent. One place these compounds can be found is in the form of secondary compounds in plants. In this experiment, the antibacterial effects of certain plant-produced compounds on gram-positive and gram-negative bacteria were explored. The results of this study may lead to clues for designing new antibiotics for harmful antibiotic-resistant bacteria. In this study, 20 plants that produced mainly secondary compounds in the terpene, phenolic, alkaloid, and organosulfur groups were tested for antibacterial properties through the measurement of zones of inhibition. Extracts were made for each plant using polar water and non-polar acetone as solvents. The extracts were then tested on gram-positive bacteria Micrococcus luteus and gram-negative bacteria Serratia marcescens. As predicted, bacteria were inhibited by compounds in extracts from each class of molecule tested, with compounds in the green tea water solution being the most effective, followed in order by the black pepper acetone solution, the onion water solution, and the ginger water solution.