GC-TOF-MS-based metabolomics correlated with bioactivity assays unveiled seasonal variations in leaf essential oils of two species in Garcinia L.

Abstract

The genus Garcinia L. is known for its many practical uses, particularly as medicines and food. However, few studies have reported the seasonal influence on Garcinia metabolites. The objective of this study was to evaluate the seasonal effects on the chemical composition and bioactivity of Garcinia essential oils (EOs), using the native G. xanthochymus Hook.f. and endemic G. yunnanensis Hu in southwest China. Gas chromatography time-of-flight mass spectrometry-based metabolomics uncovered qualitative and quantitative variations of 118 EO compounds, mainly comprising sesquiterpene hydrocarbons, oxygenated sesquiterpenes and esters. Chemometric approaches, including principal component analysis and partial least-squares-discriminant analysis (PLS-DA), further indicated that EO profiles varied distinctly according to seasons. From PLS-DA models built on seasonal samples, a total of 15 differential compounds, such as ethyl palmitate and β-bisabolene, were characterized from G. xanthochymus and 19 compounds, including pentadecane and hexadecanoic acid, from G. yunnanensis. Biological assays demonstrated that the bioactivities of leaf EOs from both species were also notably affected by seasonality. The most promising season to harvest Garcinia leaves for their cytotoxic and anti-inflammatory EOs is winter, with IC50 values lower than 20 μg/mL; for antibacterial, it is spring with MIC50 values lower than 135 μg/mL against Listeria monocytogenes. Correlation analysis further indicated that some EOs, such as β-copaene, β-bisabolene and hexadecanoic acid, were positively associated with the observed bioactivity results. These findings, taken together, suggest that EOs from Garcinia leaves have strong biological activities, but their seasonal variation needs to be carefully considered for future product development.