Chemistry and Antimycotic Potential of Nanoemulsions of Lemongrass Oil
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Date
2020
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Punjab Agricultural University, Ludhiana
Abstract
Medicinal and aromatic plant botanicals such as essential oils and extracts exhibit wide range of biological properties. Apart from their use for herbal traditional medicines, these have been utilized for food safety applications for combating toxic effects of synthetic fungicides in fruits and vegetables. Kinnow is amongst one of the most perishable commodities prone to postharvest losses due to fungal contamination and attack. The present study was aimed to develop Lemongrass essential oil (EO) based nanoemulsions against Penicillium digitatum, the post-harvest fungal pathogen of kinnow. Lemongrass (Cymbopogon flexuosus), a tall, perennial grass, contains EO which exhibits promising antimycotic potential against P.digitatum. Lemongrass EO was extracted by using Clevenger-type apparatus with per cent yield of 1.33%. Compositional analysis of extracted EO by GC-MS revealed presence of 65 compounds with Citral (77.02%) being the major compound. Lemongrass EO (LGO) nanoemulsions were prepared with Smix (Tween 80: Span 80 in 3:1) using ultrasonication treatments (three sonication timings of 10, 15 and 20 min). The coarse emulsions were prepared with oil: Smix ratio ranging from 1:0.5 to 1:4 and sonication resulted in development of nanoemulsion with droplet diameters ranging between 60.5-267.9 nm. All the nanoemulsions exhibited PDI in the range of 0.12-0.32 indicating better homogeneity. The prepared nanoemulsions were characterized for physical-chemical (pH, electrical conductivity and viscosity) and morphological properties (optical and Transmission electron microscopy). The pH and electrical conductivity of prepared nanoemulsions ranged from 4.75-6.15 and 134.9-350.0 μS cm-1 respectively. The nanoemulsions with oil: Smix ratio of 1:1 sonicated for 15 min showed the least droplet diameter and PDI. Evaluation of antimycotic potential of LGO nanoemulsions using poisoned food technique revealed the best efficacy of 1:1 ratio with sonication treatment for 15 min to inhibit growth of P. digitatum (98.5%) compared to pure LGO(75.2%) treatment. Optical microscopy of treated fungus indicated change in morphology with decrease in hyphal diameter of fungus treated with LGO and its nanoemulsions. Therefore, lemongrass essential oil nanoemulsions can be possibly used as a substitute for synthetic fungicide treatment for enhancing shelf life of stored kinnow fruits.