Isolation and extraction of antimicrobial substances against oral bacteria from lemon peel

We have isolated 4 antibacterial substances that were active against the oral bacteria that cause dental caries and periodontitis, such as Streptococcus mutans, Prevotella intermedia, and Porphyromonas gingivalis, from lemon peel, a waste product in the citrus industry. The isolated substances were identified as 8-geranyloxypsolaren, 5-geranyloxypsolaren, 5-geranyloxy-7-methoxycoumarin, and phloroglucinol 1-β-D-glucopyranoside (phlorin) upon structural analyses. Among these, 8-Geranyloxypsolaren, 5-geranyloxypsolaren, and 5-geranyloxy-7-methoxycoumarin exhibited high antibacterial activity. These 3 compounds were effectively extracted using ethanol and n-hexane, whereas phlorin was extracted with water. Further, the above 3 compounds were present in lemon essential oil and abundantly present in the residue produced upon the cooling treatment of concentrated lemon essential oil.