Acidolysis-dominated pretreatment elevates distillation yield and impacts composition, antioxidant and antifungal activities of essential oil from Cuminum cyminum seeds

Abstract

Proper pretreatment of herbal material containing essential oils (EOs) could enhance its volatile components release through either removing physical barriers or conquering chemical bonds and thereby improve hydrodistillation yield. In this regard, a trial pretreatment including pulverization, enzymolysis, short time microwave irradiation and acidolysis of Cuminum cyminum seeds was integrated into the essential oil (EO) preparation to elevate the EO yield. On the basis of Plackett–Burman design analysis, three parameters (acidolysis duration, HCl concentration of acidolysis and sieving mesh) were significant for the EO preparation. Box–Behnken design based optimization of the remaining factors concluded that the optimal pretreatment was pulverizing the seeds to 40 mesh and implementing 45 min acidolysis in 2.5 M L⁻¹ HCl wherein the predicted EO yield of 3.78% was close to that of the experimental value 3.86%. This pretreatment produced an EO yield increase of 50.78% over the control sample of raw seeds (2.56%). In total 53 components were identified in the acidolysis-pretreated cumin EO (AEO) whilst 47 components were identified in the control cumin EO (CEO). In both AEO and CEO, cuminaldehyde was the predominant common component, but the AEO contained more phenols (0.51% vs. 0.18%) and alcohols (7.76% vs. 0.18%) than the CEO did. The compositional features gave the AEO mightier antioxidant potency and stronger antifungal efficacy against four postharvest fungi, viz. Alternaria alternata, Penicillium expansum, Trichothecium roseum and Fusarium sulphureum, as compared with the situations of CEO. In conclusion, the pretreatment elevates the hydrodistillation yield, modifies the EO chemical profiles and confers stronger antioxidant and antifungal activities upon cumin EO.