Comparative Analysis of Volatile Oils from Fresh and Grilled Citrus hystrix Peels: Phytochemicals and Antifungal Activity

Abstract

In Thai traditional medicine, grilled fruits of Citrus hystrix DC. are halved and applied to the scalp for anti-dandruff, anti-itching, and hair nourishment purposes. However, no studies have reported phytochemical profile and antifungal activity of volatile oil extracted from peels of grilled C. hystrix fruits. This study aimed to analyze phytochemical profile and evaluate antifungal activities against cutaneous pathogenic fungi as Candida albicans, Candida tropicalis, Trichophyton rubrum, Trichophyton mentagrophytes, Microsporum canis, and Nannizzia gypsea of volatile oil extracted from peels of grilled C. hystrix fruits (G-ChVO) in comparison with those extracted from fresh peels (F-ChVO). Chemical composition of the volatile oils was determined using GC-MS. The analysis revealed that F-ChVO contained β-pinene (22.02%), D-limonene (18.22%), and terpinen-4-ol (11.54%), whereas G-ChVO contained β-pinene (7.66%), D-limonene (10.86%), and terpinen-4-ol (23.93%). The grilling process reduced content of β-pinene and D-limonene while content of terpinen-4-ol was increased. Antifungal activities were assessed using disk diffusion method with different concentrations of volatile oils and incubation periods. G-ChVO exhibited significantly the growth inhibitory activity against all six pathogenic fungi greater than F-ChVO. At a concentration of 10 μL/disc and incubation period of 5 days, G-ChVO demonstrated the highest antifungal activity, particularly against C. albicans. Thus, the grilling process altered chemical composition in volatile oils, leading to enhanced antifungal activity. The volatile oils extracted from the peels of grilled C. hystrix fruits have potential as a natural antifungal agent against cutaneous pathogenic fungi.