Measurement of Antioxidant Activity and Antioxidant Compounds under Versatile Extraction Conditions: I. The Immuno-Biochemical Antioxidant Properties of Sweet Cherry (Prunus avium) Extracts

Abstract

Previously, we have meticulously examined the efficacy of the measurable antimicrobial activity of sweet cherry (Prunus avium) extracts on a wide spectrum of gram-positive and gram-negative bacteria, in addition to the fungus, Candida albicans, a priori. In order to further understand the biochemical constituents and antioxidant activities of a variety of extracts of sweet cherries, antioxidant compounds of immunological significance, including L-ascorbic acid (vitamin C), phenols, flavonoids, and anthocyanins, and the total antioxidant (free radical scavenging) activity were simultaneously measured under varying and versatile extraction conditions (mild heating [5, 10 and 20 min.], and brief microwave exposure [1, 2 and 5 min.]) for a variety of extracts: i) whole juice extracts (WJE), ii) methanol-extracted juice (MEJ), iii) ddH2O-extracted pomace (dPOM), and iv) methanol-extracted pomace (mPOM). The antioxidant activity under the versatile extraction conditions adopted in this study was conspicuously reduced, such that the % inhibition against 2,2- diphenyl-1-picrylhydrazyl (DPPH) followed an inverse, negative correlational trendline. Moreover, ascorbic acid content was not affected with mild to prolonged heating or microwave exposure, except tangibly with dPOM and mPOM. The total phenols content assessed showed no significant variations, as compared with control extracts. In a manner similar to ascorbic acid, total flavonoids were mildly reduced under varying conditions, an effect mimicked to a certain extent with anthocyanins. Assessment of extraction means as compared with WJE revealed sharp decrease in the antioxidant activity for dPOM and mPOM, significant increase in L-ascorbic acid, total phenol, and flavonoid contents for MEJ, dPOM, and mPOM, and mild decrease in anthocyanin contents for dPOM and mPOM. These results confirm the measurable antioxidant activities and contents of P. avium extracts under versatile conditions of mild exposure, an effect bearing significant biochemical properties of a variety of extraction methods. Further studies are currently investigating the effect of specific antioxidants of P. avium on microbial growth in vitro per se. Since many of the aforementioned molecules hold immunobiochemical constituencies, antioxidant compounds in sweet cherries may have putative anti-inflammatory potential in medicinal chemistry, corroborating the observation of regulating/attenuating the growth of microorganisms of medical importance in vitro.