Impact of Different Drying Temperatures on In Vitro Antioxidant and Antidiabetic Activities and Phenolic Compounds of Wild Guava Leaves Collected in the Central Highland of Vietnam

Abstract

Most biologically natural compounds are very sensitive and easily degradable under drying conditions. This study aimed to investigate the effect of drying temperature on the contents of phenolic compounds and in vitro antioxidant and antidiabetic activities of wild guava leaves. Wild guava leaves were dried at 40 °C, 50 °C, 60 °C, 70 °C, and 80 °C, as well as sun drying (SD). The total phenolic and flavonoid contents (TPC and TFC) were measured using the colorimetric method. Antioxidant activity was determined by the 2,2-diphenyl-2-picrylhydrazyl hydrate (DPPH) and 2,2-azino-bis(3-ethylbenzothazoline-6-sulfonic acid (ABTS) radical scavenging activity assays. In vitro antidiabetic activity was measured by assessing α-glucosidase and α-amylase inhibitory activities. The contents of individual phenolic compounds were determined using ultra-performance liquid chromatography (UPLC). The principal component analysis (PCA) results revealed that hot air drying at different temperatures had significantly different effects on the bioactive compounds and biological properties of guava leaves. Drying at high or low temperatures resulted in a higher degradable rate of bioactive compounds leading to a weakening of the biological properties. Drying at 50 °C resulted in high TPC and TFC as well as the highest in vitro antioxidant and antidiabetic activities. Furthermore, the highest contents of gallic acid, catechin, rutin, quercetin, apigenin, quercitrin, vitexin, and apigenin-7- O-D-glucopyranoside were found in samples dried at 50 °C, whereas the highest contents of chlorogenic acid, epicatechin, and ellagic acid were observed in samples dried at 60 °C. Therefore, drying at 50 °C was the suitable temperature for retaining valuable biological compounds in wild guava leaves.

Silk nanoparticles for the protection and delivery of guava leaf ( Psidium guajava L.) extract for cosmetic industry, a new approach for an old herb

“…Since high temperature treatment (i.e. 70 °C) has been proven to statistically degrade the guava leaf polyphenol content, namely gallic acid, catechin, epicatechin, quercetin, and chlorogenic acid (Nguyen et al., 2022 ), our results prove that the SFNs played an important role in encapsulating and protecting the phenolic compounds of guava leaves extract against high temperature.…”

In vitro and in vivo antioxidant and antihyperglycemic potentials of phenolic fractions of Syzygium zeylanicum (L.) DC trunk‐bark

“…The inhibition of α‐amylase and α‐glucosidase activities was measured using the methods reported in a previous publication (Nguyen, Huyen, et al, 2022).…”

“…The phenolic constituents in the extract and its fractions were figured out using the Thermo‐Ultimate 3000UPLC system (Thermo Scientific) with the gradient method as described by Nguyen, Huyen, et al (2022).…”

“…The capacity of DPPH • and ABTS •+ radical scavenging was evaluated using the approach outlined in a previous study (Nguyen, Huyen, et al, 2022).…”

“…The inhibition of α-amylase and α-glucosidase activities was measured using the methods reported in a previous publication (Nguyen, Huyen, et al, 2022). Zebrafish (Danio rerio) were supplied by Laboratory Animals at the Biotechnology Centre of Ho Chi Minh City and reared in standard conditions according to the laboratory using standards for zebrafish (Westerfield, 2000).…”