In Vitro α-Amylase and α-Glucosidase Inhibitory Potential of Green Banana Powder Extracts.

This study investigated the proximate composition and inhibitory potential of hot water and ethanolic extracts of the pulp, peel and whole fruit of green banana (Musa sapientum) on α-amylase and α-glucosidase. Bioactive compounds were identified using GC-MS analysis. In addition, the cytotoxic effect on human gingival fibroblast (hGF) was evaluated using the sulphorhodamine B (SRB) assay. The results showed that the peel of green banana had the highest amount of ash (10.05%), fat (2.83%), protein (3.64%) and total dietary fibre (36.62%). The carbohydrate content of the whole fruit (81.79%) and pulp (81.50%) was higher than that of the peel (71.90%). The moisture content of the pulp (13.08%) was higher than that of the peel (11.58%) and whole fruit (11.30%). The ethanolic green banana peel extract showed a good inhibitory effect of α-amylase and α-glucosidase with the concentration necessary for 50% inhibition (IC50) of 0.512 and 0.100 mg·mL-1, respectively. The α-glucosidase inhibitory effect of the ethanolic green banana peel extract and the hot water green banana peel extract was not significantly different from that of acarbose (IC50 0.108 mg·mL-1). GC-MS analysis of the ethanolic green banana peel extract revealed fatty acids and fatty acid ester (9-octadecenamide (Z), octadecanamide and other compounds). The ethanolic peel extract exhibits a significant noncytotoxicity effect on hGF cells at concentrations ranging from 0.0001 to 1.0 mg·mL-1.

Evaluation of Antioxidant Activities and Tyrosinase Inhibitory Effects of Ginkgo biloba Tea Extract.

Ginkgo biloba L. (Ginkgoaceae) is one of the best-selling products, popular in nutritional properties and health benefits. In the present study, the total phenolic compounds and flavonoid content of the ethanolic extract from G. biloba tea were also evaluated. Furthermore, the antioxidant activity was determined using DPPH assay and tyrosinase inhibitory activity was also determined with L-DOPA as a substrate. The extract showed the total phenolic compound and flavonoid content were 14.13 mg GE g-1 extract and 71.33 mg rutin equivalence g-1 DW, respectively. Taking into account the results of the DPPH, the antioxidant property at the concentration of 500 µg ml-1 was 95.29% that is similar to that of the BHT, ascorbic acid, and gallic acid used as positive controls. The inhibitory capacity of the sample against tyrosinase is lower than that of positive controls at all concentrations. The results of inhibition in terms of IC50 confirm the inhibition patterns. On the other hand, the statistical similarity of the anti-DOPA auto-oxidation (IC50) of G. biloba leaf extract and kojic acid was found (456.27 and 418.5 µg ml-1) but was lower than that of ascorbic acid (IC50 989.61 µg ml-1). A relationship was observed between the potential of antioxidant activity, tyrosinase inhibition, and anti-DOPA auto-oxidation with concentration levels of the extracts. The results of phytochemical analysis revealed the presence of tannins, flavonoids, terpenoids, and reducing sugars.

Genome shuffling enhances lipase production of thermophilic Geobacillus sp.

Thermostable lipases are potential enzymes for biocatalytic application. In this study, the lipase production of Geobacillus sp. CF03 (WT) was improved by genome shuffling. After two rounds of genome shuffling, one fusant strain (FB1) achieved increase lipase activity from the populations generated by ultraviolet irradiation and ethyl methylsulfonate (EMS) mutagenesis. The growth rate and lipase production of FB1 increased highest by 150 and 238 %, respectively, in comparison to the wild type. The fusant enzyme had a significant change in substrate specificity but still prefers the long-chain length substrates. It had an optimum activity at 60 °C, pH at 7.0-8.0, with p-nitrophenyl palmitate (C16) as a substrate and retained about 50 % of their activity after 15 min at 70 °C, pH 8.0. Furthermore, the fusant lipase showed the preference of sesame oil, waste palm oil, and canola oil. Therefore, the genome shuffling strategy has been successful to strain improvement and selecting strain with multiple desirable characteristics.

Adenosine deaminase from Streptomyces coelicolor: recombinant expression, purification and characterization.

The sequencing of the genome of Streptomyces coelicolor A3(2) identified seven putative adenine/adenosine deaminases and adenosine deaminase-like proteins, none of which have been biochemically characterized. This report describes recombinant expression, purification and characterization of SCO4901 which had been annotated in data bases as a putative adenosine deaminase. The purified putative adenosine deaminase gives a subunit Mr=48,400 on denaturing gel electrophoresis and an oligomer molecular weight of approximately 182,000 by comparative gel filtration. These values are consistent with the active enzyme being composed of four subunits with identical molecular weights. The turnover rate of adenosine is 11.5 s⁻¹ at 30 °C. Since adenine is deaminated ∼10³ slower by the enzyme when compared to that of adenosine, these data strongly show that the purified enzyme is an adenosine deaminase (ADA) and not an adenine deaminase (ADE). Other adenine nucleosides/nucleotides, including 9-ß-D-arabinofuranosyl-adenine (ara-A), 5'-AMP, 5'-ADP and 5'-ATP, are not substrates for the enzyme. Coformycin and 2'-deoxycoformycin are potent competitive inhibitors of the enzyme with inhibition constants of 0.25 and 3.4 nM, respectively. Amino acid sequence alignment of ScADA with ADAs from other organisms reveals that eight of the nine highly conserved catalytic site residues in other ADAs are also conserved in ScADA. The only non-conserved residue is Asn317, which replaces Asp296 in the murine enzyme. Based on these data, it is suggested here that ADA and ADE proteins are divergently related enzymes that have evolved from a common α/ß barrel scaffold to catalyze the deamination of different substrates, using a similar catalytic mechanism.