Leptospermum petersonii (family Myrtaceae) is often cultivated for ornamental purposes but also serves as a rich source of bioactive essential oils.While several studies focused on the activities of the essential oils, this study analysed the potential of spent L.petersonii leaves as strawberry milk toner ion a natural food preservative.
Method: We investigated the in vitro antioxidant and antimicrobial activities of crude L.petersonii extracts against activities of the purified isolated flavonoid, 6-methyltectochrysin, which was characterized using spectroscopic methods.The antioxidant assays followed ORAC, FRAP and TEAC tests.
The antimicrobial activities of the extract and purified flavonoid were analysed against six multi-drug resistant microbial strains in broth dilution assays.Result: The results revealed that both the crude extracts and isolated 6-methyltectochrysin exhibited positive radical ion scavenging antioxidant potential, however the crude extract was about 6-fold more potent antioxidant than the purified 6-methyltectochrysin.The crude extract also showed strong antimicrobial activities against Bacillus cereus, and even more potent antimicrobial agent than the reference ampicillin antibiotic against Klebsiella pneumoniae subsp.
pneumoniae.A higher resistance was observed for the tested Gram-negative jilungin dreaming tea strains than for the Gram-positive ones.6-methyltectochrysin was generally inactive in the antimicrobial assays.
Conclusion: The crude methanolic extract showed significant bioactivity which validates the medicinal relevance of the plant.The observed biological activities, especially against a notorious strain of B.cereus, suggest that L.
petersonii could be a promising natural source of food preservatives.