Evaluation of chemical composition, antioxidant, antibioflm and antibacterial potency of essential oil extracted from gamma irradiated clove (Eugenia caryophyllata) buds

Abstract

The efficacy of γ-rays is known as a method for decontamination of food, herbs and spices. In the present study, clove buds (CB) were irradiated at 10 kGy by 60Co irradiator. Essential oils (EOs) recovered from un-irradiated CB and irradiated (ICB) were evaluated for their chemical composition by GC–MS, antioxidant, antibiofilm and antibacterial activity. The minimum inhibitory concentration (MIC) and growth curves against four tested multi-drug resistant (MDR) bacterial pathogens; S. aureus, B. cereus, E. coli and K. pneumoniae were also evaluated. The liberation of cellular contents, as well as the alterations in cell membrane permeability, together with ultrastructural changes in the pathogen morphology, have been evaluated utilizing spectrophotometer, scanning electron microscope (SEM) and energy dispersive X-ray fluorescence spectrometry (EDXFS). Results revealed that EOs recovered from ICB leads to a rise in the phenolic and flavonoid contents by 3.82 and 3.44 mg/g of oil, respectively. Antioxidant potency was elevated by 6.63% for ICB recovered EOs compared to EOs from CB. Antibiofilm and antibacterial activities were improved against all tested MDR pathogens accompanied by decline in their cell growth. The MIC of EOs recovered from ICB raised up the release of bacterial intracellular proteins and DNA/RNA contents significantly (p < 0.05) in time dependent manner. The leakage of bacterial contents had been supported by the increase in the release of C, O, N, P, Mg with presence of new elements (Ca and S) in S. aureus treated with MIC of EOs recovered from ICB. Moreover, cell wall/membrane damages and shrinkage in S. aureus cells was clearly observed in SEM images. This study concluded that γ-rays at dose 10 kGy has a significant potential to stimulate antioxidant, antibiofilm and antibacterial potency of EOs recovered from CB due to increase in phenolic and flavonoid contents. This could improve the uses of EOs recovered from ICB will support the efforts to find a natural and more potent antioxidant, antibiofilm, and antibacterial against MDR pathogens, which is useful in food and pharmaceutical industries.