Chemical Composition of a Supercritical Fluid (Sfe-CO<sub>2</sub>) Extract from <i>Baeckea frutescens</i> L. Leaves and Its Bioactivity Against Two Pathogenic Fungi Isolated from the Tea Plant (<i>Camellia sinensis</i> (L.) O. Kuntze)
Hao Jiang | Mengting Zhang | Li Qin | Dongxu Wang | Feng Yu | Wenhui Liang | Chuankui Song | Daniel Granato
<i>Colletotrichum gloeosporioides</i> and <i>Pseudopestalotiopsis camelliae-sinensis</i> are the two most important tea plant (<i>Camellia sinensis</i> L.) pathogenic fungi. Interest in natural plant extracts as alternatives to synthetic chemical fungicides to control plant pathogens is growing. In this study, the volatile fraction of <i>Baeckea frutescens</i> L. was extracted by supercritical fluid extraction (SFE-CO<sub>2</sub>), and its chemical composition was analyzed, and investigated for its antifungal activity against <i>C. gloeosporioides</i> and <i>P. camelliae</i>. The major constituents of the volatile fraction were β-caryophyllene (28.05%), α-caryophyllene (24.02%), δ-cadinene (6.29%) and eucalyptol (5.46%) in <i>B. frutescens</i> SFE-CO<sub>2</sub> extracts. The terpineol, linalool, terpinen-4-ol and eucalyptol showed strong contact antifungal activity against <i>P. camelliae</i> and <i>C. gloeosporioides</i> with median inhibitory concentration (MIC<sub>50</sub>) in the range of 0.69 μL/mL to 2.79 μL/mL and 0.62 μL/mL to 2.18 μL/mL, respectively. Additionally, the volatile fraction had high fumigation antifungal activity against <i>P. camelliae</i> and <i>C. gloeosporioides</i> with an inhibition rate between 20.87% and 92.91%. Terpineol presented the highest antifungal activity in the contact and fumigation toxicity assays. Terpineol, linalool, terpinen-4-ol and eucalyptol were associated with the most active chemical compounds in the volatile fraction against the fungi. The results suggest that <i>B. frutescens</i> SFE-CO<sub>2</sub> extracts are potential ingredients to develop a natural fungicide for control of tea plant pathogens.
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