Active compounds of Michelia champaca bark extract against Curvularia verruculosa fungi causing leaf spot disease in rice (Oryza sativa L.)

Abstract

Curvularia verruculosa fungal causes leaf spot disease in rice plants. The bark extract of Michelia champaca could inhibit the growth of the fungi. The present research aimed to know the active compound responsible for antifungal activity. Extraction was done using the Maceration method, antifungal activity was measured using the Diffusion well method, and identification of active compounds was carried out using Gas chromatography-mass spectroscopy (GC-MS). The methanol extract obtained had a yield of 18.7%. It showed strong activity against C. verruculosa with an inhibition zone until 30.01 mm. The fractionation results showed that n-hexane extract (HE) was the strongest inhibiting the growth of C. verruculosa (32.45 mm), followed by chloroform extract (CE) (29.20 mm), while n-butanol extract (BE) was not active. Separating active compounds from HE extract was made using Column chromatography (CC) method with silica gel as the stationary phase and the mixture of n-hexane-acetone (3:1) as the mobile phase. This separation resulted in 5 combined fractions; HE3 and HE5 extracts showed very strong activity against C. verruculosa, with a diameter of the inhibition zone of 26.73 and 33.46 mm, respectively; HE2 extract showed strong activity with a diameter of the inhibition zone of 15.21 mm, while HE1 and HE4 extracts did not show activity. Identification using GC-MS, especially the HE3 extract, revealed that the extract contained two compounds: tributyl acetyl citrate and terephthalic acid, dodecyl-2-ethylhexyl ester. The result indicated that the bark extract of M. champaca had the potential to be a botanical fungicide.