Varietal Influences on Antihyperglycemia Properties of Freshly Harvested Apples UsingIn VitroAssay Models

Abstract

The well-known health benefits of apples have been attributed in part to the presence of polyphenols and related antioxidant capacity. The consumption of apples could provide health benefits by reducing the risk for chronic diseases such as metabolic syndrome disease, including type 2 diabetes. Thus, the objective of this study was to investigate the phenolic-linked antihyperglycemia bioactive factors in aqueous and 12% ethanol extracts of peel and pulp from 10 different freshly harvested apple varieties commonly consumed in the United States. The extracts were analyzed for total soluble phenolics, 2,2-diphenyl-1-picrylhydrazyl-linked antioxidant activity, and their associated in vitro α-glucosidase and α-amylase inhibitory activities. In general, peel extracts had higher total soluble phenolic content and related antioxidant capacity than pulp extracts. Quercetin derivatives, protocatechuic acid, chlorogenic acid, and p-coumaric acid were detected, and the amount varied significantly between aqueous and ethanolic extracts. Honeycrisp and Red Delicious varieties had the highest total phenolic contents and a significant correlation with antioxidant capacity (r = 0.91). In addition, high α-amylase and α-glucosidase inhibitory activities in aqueous pulp extracts were found. However, the peel extracts had the highest α-glucosidase inhibitory activity along with low α-amylase inhibitory activity. No correlation between α-amylase inhibitory activity and total phenolic content was observed. However, positive correlations between α-glucosidase inhibitory activity and total phenolics in aqueous (r = 0.50) and ethanolic (r = 0.70) extracts were observed. This study provides the biochemical rationale for animal and clinical studies to determine the suitable varieties with optimum bioactive factors with antihyperglycemia potential.

INFLUENCE OF VARIETAL AND pH VARIATION ON ANTIHYPERGLYCEMIA AND ANTIHYPERTENSION PROPERTIES OF LONG-TERM STORED APPLES USING IN VITRO ASSAY MODELS

“…Among pulp extracts, the total phenolic content ranged from 30 (Empire) to 60 µg (Red Delicious) GAE/g FW for aqueous extracts and from 47 (Empire) to 133 µg (Red Delicious) GAE/g FW for ethanolic extracts. Red Delicious is a good apple cultivar with similar high total phenolic content when compared with our previous work on freshly harvested apples (Barbosa et al . 2010) and, therefore, storage conditions retained the overall phenolic content.…”

“…Both aqueous and ethanolic pulp extracts had low antioxidant capacity (7–32%) compared with peel extracts. Barbosa et al . (2010) found similar range for DPPH inhibition in freshly harvested apples and, therefore, storage condition retained the antioxidant functionality.…”

“…Previous in vitro studies have shown that freshly harvested apples have phenolic‐linked bioactives that have the potential for managing hyperglycemia linked to type 2 diabetes (Adyanthaya et al . 2009; Barbosa et al . 2010).…”

“…In these fresh apple studies, several cultivars showed phenolic‐linked antihyperglycemia potential (Adyanthaya et al . 2009; Barbosa et al . 2010).…”

Studying the interactions between tea polyphenols and α-amylase

“…Interestingly, the observed inhibitory effect was not dependent on the total phenolic content levels of the apple juice varieties, which is not in agreement with a positive correlation between α-amylase inhibitory activity and total phenolic content (Barbosa, Pinto, Sarkar, Ankolekar, Greene, & Shetty, 2010). This may result from the variances of some single phenolic compounds which have inhibitory effect on α-amylase, such as chlorogenic acid (Narita & Inouye, 2011), caffeic acid (Narita & Inouye, 2011), and flavan-3-ols (Gamberucci, Konta, Colucci, Giunti, Magyar, Mandl, et al, 2006).…”