STACHYS BYZANTINA LEAVES: PHYTOCHEMICAL ANALYSIS, 𝜶 -AMYLASE INHIBITION, AND DIGESTIBILITY EVALUATION OF PHENOLICS, FLAVONOIDS AND ANTIOXIDANT ACTIVITY

The Lamiaceae family is notable for its antioxidant and bioactive potential, as exemplified by Stachys byzantina K. Koch, a species traditionally used for medicinal and dietary purposes. Its pharmacological effects are attributed to phytochemicals capable of modulating oxidative stress and inhibiting enzymes involved in carbohydrate metabolism. However, the efficacy of these compounds depends on their bioavailability throughout the gastrointestinal tract, and there is a gap in the literature regarding simulated digestibility in this species. Therefore, the objectives of this study were to investigate the phytochemical profile, quantify bioactive compounds, evaluate α-amylase inhibitory capacity, and investigate the stability of total phenolic compounds (TPC), total flavonoids (TFC), and antioxidant activity (AA) during in vitro digestion. Freeze-dried and ground leaves of S. byzantina were subjected to phytochemical screening and quantification of phenolics by HPLC-PDA. The hypoglycemic potential of the aqueous and 80% ethanolic extracts (1:24m/v) was evaluated via α-amylase inhibition. The bioaccessibility of TPC, TFC, and AA, after simulated digestion, was evaluated using the INFOGEST protocol. Statistical analysis was performed using ANOVA and Tukey’s test (p≤0.05). Phytochemical screening revealed the presence of flavonoids, triterpenes, coumarins, iridoids, and anthraquinones. Significant levels of catechin (240.26mg/g) and quercetin (12.36mg/g) were quantified, in addition to cinnamic acid (5.43mg/g) and gallic acid (0.11mg/g). The extracts demonstrated marked hypoglycemic activity by inhibiting α-amylase at 0.25mg/mL, with the aqueous extract (95.18%) showing superior activity to the ethanolic extract (88.00%), which can be attributed to the ability of catechins, quercetin, tannins, and triterpenes to block the enzyme’s catalytic site. During digestion, the gastric phase exhibited high bioaccessibility in all assays, preserving 82.9% of the TPC (17.38mgEAC/g) and 49.7% of the TFC (47.20mgCE/g). Although flavonoids are typically unstable under gastric acidity, the plant matrix ensured significant preservation of these compounds. In the AA assessment, bioaccessibility values were also significant: 78.0% for DPPH (9.16µmolTE/g), 67.6% for ABTS (4.77µmolTE/g), and 73.1% for FRAP (6.92µmolTE/g). This gastric stability is facilitated by matrix-dependent structural changes under acidic pH conditions. Upon reaching the intestine, TPC maintained a bioaccessibility of 59.9% (12.57mgEAC/g) and DPPH of 75.0% (8.86µmolTE/g). Although TFC (40.4%; 38.37mgCE/g), ABTS (17.3%; 1.22µmolTE/g), and FRAP (26.4%; 2.50µmolTE/g) showed expected decreases due to the slightly alkaline intestinal pH and complexation with plant matrix fibers characteristic of this species, data demonstrate the high stability and bioaccessibility of the phytochemicals. Taken together, the findings highlight the potential of S. byzantina as a source of compounds with antioxidant activity and enzyme-inhibitory capacity, with promising applications in the pharmaceutical and food industries. Further studies are recommended to investigate the effects of thermal processing and conduct in vivo assays to evaluate enteric absorption and gut microbiota interactions. 

Financial support: CAPES (PNPD and Demanda Social Program, Finance Code 001)