Phenolic Content, Antioxidant, Antibacterial, Antihyperglycemic, and α-Amylase Inhibitory Activities of Aqueous Extract of Salvia lavandulifolia Vahl

Abstract

Salvia lavandulifolia Vahl essential oil is becoming more popular as a cognitive enhancer and treatment for memory loss. It is high in natural antioxidants and has spasmolytic, antiseptic, analgesic, sedative, and anti-inflammatory properties. Its aqueous extract has hypoglycemic activity and is used to treat diabetic hyperglycemia, but few studies have focused on it. The objective of this work is to evaluate the various biological and pharmacological powers of Salvia lavandulifolia Vahl leaf aqueous extract. Quality control of the plant material was first carried out. Followed by a phytochemical study on the aqueous extract of S. lavandulifolia leaves, namely phytochemical screening and determination of total polyphenols, flavonoids, and condensed tannins contents. Then, the biological activities were undertaken, in particular the antioxidant activity (total antioxidant activity and trapping of the DPPH° radical) and the antimicrobial activity. The chemical composition of this extract was also determined by HPLC-MS-ESI. Finally, the inhibitory effect of the α-amylase enzyme as well as the antihyperglycaemic effect was evaluated in vivo in normal rats overloaded with starch or D-glucose. The aqueous extract obtained by use of the decoction of leaves of S. lavandulifolia contains 246.51 ± 1.69 mg EQ of gallic acid/g DE, 23.80 ± 0.12 mg EQ quercetin/g DE, and 2.46 ± 0.08 mg EQ catechin /g DE. Its total antioxidant capacity is around 527.03 ± 5.95 mg EQ of ascorbic acid/g DE. At a concentration of 5.81 ± 0.23 µg/mL, our extract was able to inhibit 50% of DPPH° radicals. Moreover, it showed bactericidal effect against Proteus mirabilis, fungicidal against Aspergillus niger, Candida albicans, Candida tropicalis, and Saccharomyces cerevisiae, and fungistatic against Candida krusei. A marked antihyperglycemic activity (AUC = 54.84 ± 4.88 g/L/h), as well as a significant inhibitory effect of α-amylase in vitro (IC50 = 0.99 ± 0.00 mg/mL) and in vivo (AUC = 51.94 ± 1.29 g/L/h), is recorded in our extract. Furthermore, its chemical composition reveals the presence of 37.03% rosmarinic acid, 7.84% quercetin rhamnose, 5.57% diosmetin-rutinoside, 5.51% catechin dimer, and 4.57% gallocatechin as major compounds. The antihyperglycemic and α-amylase inhibitory activities, associated with the antioxidant properties of S. lavandulifolia, justify its use in the treatment of diabetes in traditional medicine and highlight its potential introduction into antidiabetic drugs.

Phytochemical Profile, Antioxidant, Antimicrobial, and Antidiabetic Activities of Ajuga iva (L.)

“…For this reason, the oral administration of A. iva (L.) decoction, with a concentration of 40 mg/mL, 30 min before starch overload in our normal rats allowed a significant reduction in their postprandial hyperglycemia at 60, 90, and 120 min ( p < 0.001), with the respective values of 0.84 ± 0.05 g/L, 0.85 ± 0.03 g/L and 0.86 ± 0.06 g/L compared to the group pretreated with distilled water. The latter, when overloaded with starch, induced remarkable hyperglycemia at t = 60 min (1.07 ± 0.02 g/L), 90 min (1.15 ± 0.07 g/L), and 120 min (1.05 ± 0.04 g/L) [ 56 ]. On the other hand, acarbose significantly reduced postprandial hyperglycemia at 60 min ( p < 0.001, 0.89 ± 0.06 g/L), 90 min ( p < 0.001, 0.85 ± 0.08 g/L), and 120 min ( p < 0.001, 0.78 ± 0.09 g/L) over the 2 h after starch excess ( Figure 6 A).…”

“…The plates were then incubated for 24 h at 37 °C. Following incubation, MBC/MFC is found to be the lowest concentration that prevents colony formation on solid agar medium [ 56 , 57 ].…”

“…The oral starch tolerance test was carried out as follows: the product to be tested (distilled water, decoction or Acarbose) was administered (t = 0 min), 30 min later, a blood glucose measurement was performed, just after, a surplus of starch (3 g/kg) was given to the rats. After that, the blood glucose variation was assessed after 30, 60, and 120 min [ 56 ].…”

“…In order to determine the minimum bactericidal or fungicidal concentration (MBC or MFC), a volume of 10 µL was extracted from wells where no visible growth was observed, and it was subsequently inoculated on Mueller-Hinton agar plates for bacterial growth or Sabouraud agar for fungal growth. The plates were then incubated for 24 h at 37 • C. Following incubation, MBC/MFC is found to be the lowest concentration that prevents colony formation on solid agar medium [56,57].…”

“…Life 2023, 13, x FOR PEER REVIEW 21 of 27 [56]. On the other hand, acarbose significantly reduced postprandial hyperglycemia at 60 min (p < 0.001, 0.89 ± 0.06 g/L), 90 min (p < 0.001, 0.85 ± 0.08 g/L), and 120 min (p < 0.001, 0.78 ± 0.09 g/L) over the 2 h after starch excess (Figure 6A).…”