Chemical compositions and antifungal activity of Corymbia citriodora, Cupressus macrocarpa, and Syzygium cumini extracts: GC–MS and HPLC analysis of essential oils and phenolic compounds

Abstract

This study was undertaken to explore the content and the chemical constituents of the essential oils (EOs) and methanol leaf extracts (MLEs) from Corymbia citriodora, Cupressus macrocarpa, and Syzygium cumini. Chromatographic analyses of GC–MS and HPLC were used. The EOs and MLEs were prepared at concentrations of 0, 6, 12, 25, and 50 mg/L, while the extract was prepared at concentrations of 0, 500, 1000, 2000, and 4000 mg/L. Sapwood blocks of Pinus sylvestris in the dimension of 0.5 × 2 × 2 cm were prepared and autoclaved at 121 °C, and each wood block received 100 µL of the prepared concentrations from the EOs and MEs. The bioactivities of wood-treated EOs or MEs were measured against the growth of Fusarium solani MW947256. By GC–MS, the main compounds in the EOs from C. citriodora were citronellal, citronellol, p-cymene, spathulenol, and isopulegol with values of 23.95, 9.80, 9.32, 9.29, and 5.38%, respectively, in Cup. macrocarpa leaves were sabinene (11.94%), 4-terpinenol (11.34%), citronellol (9.59%), citronellal (9.85%), p-cymene (7.67%), spathulenol (5.24%), γ-terpinene (5.05%), camphor (4.31%), and limonene (3.2%), and in S. cumini leaves were trans-β-ocimene (19.11%), α-pinene (18.79%), caryophyllene (9.30%), (Z)-β-ocimene (8.16%), and limonene (6%). By HPLC, the most abundant phenolic compounds in the methanol extract from C. citriodora benzoic acid (8.11 μg/g), and gallic acid (7.96 μg/g), from Cup. macrocarpa were syringic acid (7.59 μg/g), catechol (6.85 μg/g), and gallic acid (6.78 μg/g), and from S. cumini were cinnamic acid (10.66 μg/g), caffeic acid (9.87 μg/g), and ellagic acid (8.76 μg/g). The highest percentages of inhibition (65.71% and 35.71%) against the growth of F. solani were seen in the wood treated with Cup. macrocarpa EOs at 50 and 25 mg/L, respectively. The maximum level of inhibition was seen (92.85%) when S. cumini MLEs at a dose of 4000 mg/L was applied to wood samples, followed by Cup. macrocarpa MLEs (70.00%) compared to the positive control of azoxystrobin + difenoconazole (1000 mg/L), which caused 100% inhibition to F. solani. The findings indicated that bioactive chemicals present in the extracts and EOs from these trees have strong antifungal properties.