α glucosidase

Two enzymes, namely β-glucosidase (Almond) and α- and β-glucosidase (Aspergillus niger), were obtained from Sigma Aldrich Chemie B.V. The other six enzymes (α-glucosidase (Yeast), α-glucosidase (Aspergillus niger), β-glucosidase (Aspergillus niger), β-glucosidase (Thermotoga maritima), and β-glucosidase (Phanerochaete chrysosporium)) were purchased from Megazyme (Bray, Ireland), and β-glucosidase (Bacteroides fragilis) from Prozomix Limited (Haltwhistle, UK). All enzymes tested can be considered easy to handle. More features concerning enzymes are reported in Table S1.

The content of soluble dextran produced during fermentation by W. cibaria P9 was determined by an enzyme-assisted method using a mixture of dextranase (Sigma-Aldrich, Darmstadt, Germany) and α-glucosidase (Megazyme, Bray, Ireland) according to the method reported by Katina et al. [37 (link)]. dextranase from Chaetomium erraticum and α-glucosidase from Aspergillus niger were purchased from Sigma-Aldrich (Germany). About 100 mg of freeze-dried dough was placed in 10 mL centrifuge tubes with 3 mL of water/ethanol (50:50 v/v) solution at 100 °C for 5 min. Another 3 mL of aqueous ethanol solution was added; then, the mixture was centrifuged at 10,000× g for 10 min. A further sample cleaning was made by re-suspending and centrifuging the pellet in 5 mL aqueous–ethanol solution. The pellet was re-suspended in 4.5 mL of sodium citrate buffer 0.05 M (pH 5.5) and kept at 100 °C for 5 min, vigorously vortexing after 2 min. The solutions cooled before the addition of a mixture of dextranase (100 nkat/mL) and α-glucosidase (10 nkat/mL), reaching the final volume of 5 mL with a hydrolysis temperature of 30 °C for 48 h. The reaction was stopped by keeping the samples in a boiling water bath for 10 min, after which the glucose formed was quantified using a K-GLUC glucose kit (Megazyme, Bray, Ireland).

A total of 4 kg of leaves from the plant species Psychotria malayana Jack were collected from Cermin Nan Gedang, located in the Sarolangun district of the Jambi province in Indonesia. The leaves were identified by Dr. Shamsul Khamis, a taxonomist affiliated with the University of Putra, Malaysia. The specimen with voucher number (PIIUM008-2) was deposited in the Herbarium at Kulliyyah of Pharmacy, IIUM, Kuantan. Organic solvents of analytical and chromatographic quality (ethanol, methanol, and dimethyl sulfoxide), ascorbic acid, Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), 2,4,6-Tris(2-pyridyl)-s-triazine (TPTZ), sodium chloride (NaCl), potassium chloride (KCl), calcium chloride dihydrate (CaCl₂.2H₂O), and magnesium sulphate heptahydrate (MgSO₄.7H₂O) were purchased from Merck (Darmstadt, Germany). α-Glucosidase (Megazyme, Bray, Ireland), ρ-nitrophenyl-ρ-D-glucopyranosidase (PNPG), 2,2-Diphenyl-1-picrylhydrazyl (DPPH), quercetin, phenidone, lipoxygenase, and N-trimethylsilyl-N-methyl trifluoroacetamide (MSTFA) (from Sigma-Aldrich Chemical Co., St. Louis, MO, USA) were also purchased.