Chemical Compositions, Antioxidant and Antimicrobial Activities of Essential Oils of Psidium guajava L. Leaves from Different Geographic Regions in China.

Hydrodistilled essential oils (EO) of Psidium guajava L. leaves from different regions in China were analyzed by GC and GC/MS. The samples from Guangdong Province displayed high EO yields (0.61 - 0.75%, v/w). A total of 50 components, representing over 98.00% of the EOs, were identified and semi-quantitatived. The major constituents of EOs included β-caryophyllene (17.17 - 31.38%), γ-gurjunene (9.17 - 15.22%), τ-cadinol (1.35 - 10.02%) and calamenene (2.13 - 7.80%). The terpenoids in all sample oils were dominated by sesquiterpenes hydrocarbons (70.18 - 84.35%), followed by oxygenated sesquiterpenes (9.89 - 22.19%). The similarities and differences among EOs from different samples were evaluated by hierarchical cluster analysis and principal component analysis methods. The IC50 values of EOs from different regions were between 18.52 - 33.72 mg/ml (DPPH) and 13.12 - 25.15 mg/ml (ABTS+ ). The FRAP value of EO from Guangdong Province was 7.34 - 9.13 mmol Vc/g DM, while the FRAP value of EO from Taiwan Province was 2.29 - 2.36 mmol Vc/g DM. The antimicrobial tests revealed that EO had a higher antimicrobial activity against all Gram-positive bacteria and two fungi. Moreover, EO from P. guajava leaves of Guangdong Province showed the highest antimicrobial activity. These properties can be considered in the design of industrial products and for further application in the food, pharmaceutical and cosmetic industries.