Chemical composition and antifungal activity of cuticular wax isolated from Asian pear fruit (cv. Pingguoli)

In order to understand the cuticular wax properties of Asian pear fruits (cv. Pingguoli), a series of assays was conducted on extraction, fractionation and determination of composition. The results showed that the maximum yield of wax from the fruit was obtained by chloroform/methanol (3:1), and then by chloroform extraction. Polar and low polar fractions occupied 64.3% and 26.9% of total crude wax by column chromatography. 54 and 22 components were identified in polar and low polar fractions by GC/MS, respectively. Long-chain fatty acids and triterpenoids predominated in polar fraction and n-alkanes were predominant in low polar fraction. In vitro tests indicated that polar fraction, low polar fraction and total crude wax inhibited spore germination and mycelial growth of Alternaria alternata, which is a causal agent of Alternaria rot of pears, and the maximum inhibition was obtained by polar fraction. These findings indicated that n-alkanes in low polar fraction and triterpenoids, fatty acid in polar fraction might have contributed to the antifungal properties of pear fruit cuticular waxes.

► Significant differences (P < 0.05) were found in the yields of cuticular wax extracted from the cuticles of fruits with various solvents. Chloroform/methanol (3:1) showed the most efficient extraction, and led to the highest yields.
► Polar and low polar fractions occupied 64.3% and 26.9% of total crude wax by column chromatography.
► Long-chain fatty acids and triterpenoids predominated in polar fraction and n-alkanes were predominant in low polar fraction.
► In vitro tests indicated that polar fraction, low polar fraction and total crude wax inhibited spore germination and mycelial growth of Alternaria alternata, a causal agent of Alternaria rot of pears, and the maximum inhibition was obtained by polar fraction.