Fruit of Ziziphus jujuba Mill. are used as functional foods for centuries due to their rich content and bioactivities. Although in vitro antioxidant and hypoglycaemic activity of jujube fruit were investigated previously, the bioavailability phenomenon has been disregarded so far. For this study, 80% ethanol extract of Ziziphus jujuba fruit (ZJE) was investigated for its in vitro hypoglycaemic and antioxidant potentials, before and after the interaction with simulated human digestion. DPPH scavenging activity, FRAP, CUPRAC, and TOAC assays were used for this purpose. Moreover, inhibition potentials of α-amylase and α-glucosidase enzymes and advanced glycation end products (AGE) were examined for the hypoglycaemic effect. Results indicated that ZJE showed significant antioxidant and dose dependent enzyme and AGE inhibition activity. Nonetheless, subsequent to simulated human digestion in vitro bioactivities of ZJE were significantly lowered for bioavailable fraction (IN). Protocatechuic acid (PA) (major phenolic compound of the fruit) contents of the extract and fractions were measured via HPTLC for more accurate understanding of the effects of human digestion and bioavailability profile.

Herbal infusions have become very popular due to their pleasant flavor as well as their positive influence on health. The compositions of such infusions are affected by the extraction technique, duration, additives as well as container materials. This study implements comparison of antioxidant activities and phenolic contents of the infusions commercially purchased Tilia platyphyllos Scop. samples, one of the most preferred herbal infusions worldwide, prepared by using teapots with different materials. Antioxidant potencies of the samples were examined using tests with different mechanisms such as free radical scavenging test (DPPH), metal-related activity tests (CUPRAC, FRAP). On account of assessing the phenolic profile, total phenol, phenolic acid and flavonoid contents were estimated spectrophotometrically. In addition, the presence of protocatechuic acid in the extracts was investigated by HPTLC densitometry (between 0.762-1.037 w/w%). Besides, antioxidant activities (DPPH, CUPRAC and TOAC) of the extracts were recalculated after addition of natural/synthetic sweeteners, brown and white sugar, lemon, flower and pine honeys to the infusions. Results showed that the highest total antioxidant capacity was seen on Tiliae infusions prepared in ceramic teapot (672.80±1.40 mg AAE/g DE). Moreover, stevioside addition enhanced DPPH radical scavenging of Tiliae extracts (2781.76±44.38 EC50 in μg/mL). This is the first report related with comparison of these brewing materials and additives in respect to their phenolic content and antioxidant activity of herbal teas.

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