Extraction-Dependent Antioxidant Activity of Red Horse Chestnut (Aesculus × carnea, Family Sapindaceae) Plant Parts

Horse chestnut is a rich source of active compounds that exhibit a variety of biological activities, including antioxidant, anti-inflammatory, and vascular sealing properties. The predominant variety is Aesculus hippocastanum L. (White Horse Chestnut), whereas there are limited reports regarding the biological activity, including the antioxidant potential, of the Red Horse Chestnut (Aesculus carnea H.) variety. This study aimed to conduct a comprehensive analysis of the antioxidant activity of extracts from various parts of A. carnea, including leaves, flowers, unripe, and ripe fruit, as well as to assess the total polyphenol content of the plant, given the limited number of published studies on the subject. This section of the study examined the impact of different extraction factors, including the selection of extraction techniques (Soxhlet extraction, maceration, and ultrasound-assisted extraction) and their parameters (time, solvent type, and concentration). During the second stage of the study, extracts exhibiting the highest antioxidant potential underwent phytochemical analysis utilising HPLC, which included specific phenolic acids and flavonoids. Analyses conducted revealed that extracts from unripe fruits, particularly those prepared in concentrated ethanol using the Soxhlet apparatus, exhibited the highest antioxidant potential and polyphenolic compound content. Notable findings include myricetin (322.281 ± 6.941 mg), 4-hydroxybenzoic acid (25.360 ± 0.525 mg), ferulic acid (62.690 ± 1.350 mg), epicatechin gallate (2.950 ± 0.064 mg), 2-hydroxycinnamic acid (2.013 ± 0.043 mg), ellagic acid (1.735 ± 0.037 mg), and quercetin (1.636 ± 0.037 mg). The antioxidant activity of extracts from unripe fruit, assessed using the DPPH^• method, ranged from 0.31 to 3.38 [mg ascorbic acid g^-1 of fresh raw material]. The results obtained suggest that red horse chestnut, with its significant levels of compounds exhibiting antioxidant potential, such as polyphenols, could serve as a valuable raw material for the pharmaceutical and cosmetics sectors.