Glutinous rice (Oryza sativa L.) protein extract with potent α-amylase inhibitory activity.

This research screened for α-amylase inhibitory activity of twenties-five varieties Thai indigenous rice seeds. Based on specific inhibition, crude protein of var. Gai Ngaw (Gs. No. 13719) was selected for purification. The unbound proteins of the Q-Sepharose column named partially purified rice α-amylase inhibitor (RAI) revealed MW of approximately 14.4 kDa. The RAI was stable at pH 4 to 7 and heat stable up to 80 °C. The RAI had IC50 of 15.92 ± 1.08 µg/ml. The double reciprocal plot implied a mixed-type inhibitor. The Dixon and Cornish-Bowden plots were used to estimate Ki and αKi. This suggested Thai indigenous rice seeds could potentially be developed as a food supplement for blood sugar and weight controls.

Antioxidant, antibacterial and DNA protective activities of protein extracts from Ganoderma lucidum.

Crude proteins of cultured mycelia and fruiting bodies of Ganoderma lucidum were investigated for antioxidant, antibacterial and DNA protective activities. It was found that the half maximal inhibitory concentration (IC50) of the mycelia protein and fruiting bodies protein extracts against 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) radical (ABTS(•+)) were 2.47 ± 0.01 and 2.77 ± 0.11 µg protein/ml and against 2,2-diphenylpicrylhydrazyl radical (DPPH(•)) were 2.5 ± 0.01 and 3.42 ± 0.01 µg protein/ml, respectively. The ferric reducing-antioxidant power (FRAP) values of those samples were 1.73 ± 0.01 and 2.62 ± 0.01 µmole trolox/µg protein respectively. Protein hydrolysates prepared by pronase exhibited a weaker antioxidant activity. Both crude proteins showed antibacterial activity, whereas only the mycelia protein extract could protect DNA damage by hydroxyl ((•)OH) radicals. This protein extract was partial purified by Diethyl amino ethyl (DEAE)-Sepharose column and Sulfopropyl (SP)-Sepharose column, obtained major protein with molecular weight about 45 kilo Dalton (kDa). In conclusion, G. lucidum protein extracts have promise potential for applications as antioxidant and antibacterial agents.

Decolorization of synthetic melanins by crude laccases of Lentinus polychrous Lév.

Melanins are complex natural pigments that darken the skin and are difficult to degrade. This study evaluated synthetic melanin decolorization by the crude laccase from fungus Lentinus polychrous in the absence and presence of selected redox mediators. The greatest melanin decolorization activity was 87 % at pH 6.5 within 3 h in the presence of 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS), whereas only about 22 % melanin decolorized at pH 5.0 in case of no mediator. The optimum temperatures for melanin decolorization in the absence and presence of ABTS were 55 and 35°C, respectively. Using a natural redox mediator, 1.0 mmol/L vanillin leads to 45 % melanin decolorization. Our results suggest the possibility of applying vanillin for L. polychrous laccase-catalyzed decolorization of melanin.

Antioxidant and antibacterial activities of selected varieties of thai mango seed extract.

This study reports the antioxidant and antibacterial activities of four fresh mango seed extracts from Thai varieties. Total phenol contents determined by the Folin-ciocalteu method revealed the highest values to be in MKE, Chok-a-nan variety (399.8 mgGAE/g extract) and MSE of Nam-dok-mai variety (377.2 mgGAE/g extract). Both extracts showed potent ABTS˙+ radical and DPPH˙ radical scavenging activities with the lower half inhibition concentration (IC50) values than those of the reference compounds; vitamin C, trolox and BHA, respectively. Their antioxidant property of MSE and MKE is strongly correlated with the total phenol contents (r=0.98 and 0.98, respectively). When combined the MSE and MKE of the Fah-lun variety showed the strongest antioxidant activity. All mango seed extracts showed interesting antibacterial activity against both gram positive and gram negative bacteria as determined by disc diffusion method. The most sensitive pathogenic strain inhibited by all extracts (especially Kaew variety) was Pseudomonas aeruginosa ATCC 27853. This work suggests potential applications for practical uses of mango seed extracts from Thai varieties, as sources of antioxidant and antibacterial agents.