Improving Antioxidant Activity of Ophioglossum thermale Kom. by Fermentation with Talaromyces purpurogenus M18-11

Abstract

Ophioglossum thermale Kom. was fermented with several fungi. The total phenolic and flavonoid contents (TPCs and TFCs) and antioxidant activities of fermented and non-fermented O. thermale (FOT and NFOT) were investigated. The results showed that Talaromyces purpurogenus M18-11 fermented O. thermale possessed significantly improved TPC and TFC and exhibited significantly stronger 1,1-diphenyl-2-picrylhydrazyl (DPPH) (half maximal inhibitory concentration (IC 50 ) = 75.7 ± 2.1 μg mL -1 ) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) (IC 50 = 20.52 ± 1.68 μg mL ) than original material. The determination of the contents of representative flavonoids and their glucosides revealed that the improvements are attributed to the hydrolysis of homoisoflavonoid and flavonoid glucosides, glycometabolism, as well as fungal metabolites. This paper is the first to report the fermentation of O. thermale with pure strains and T. purpurogenus is an effective strain to process O. thermale for improving the antioxidant activity. Keywords: Ophioglossum thermale, Talaromyces purpurogenus, fermentation, antioxidant activity, flavonoid IntroductionThe genus Ophioglossum (Ophioglossaceae) is a small terrestrial plant that is distributed worldwide. M18-11 J. Braz. Chem. Soc. 1928 In the present study, the herb of O. thermale was fermented with several fungi. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radicalscavenging activities, reducing power, and ferric reducing antioxidant power (FRAP) of non-fermented and fermented O. thermale (FOT) were determined for evaluating their antioxidant activities. Talaromyces purpurogenus M18-11 was screened to process O. thermale for improving the antioxidant activity. Further total phenolic and flavonoid contents (TPCs and TFCs) determination and highperformance liquid chromatography (HPLC) analysis were used for explaining the changes of antioxidant. ExperimentalChemicals ABTS, DPPH, 2,4,6-tri(2-pyridyl)-1,3,5-triazine (TPTZ), and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) were obtained from J&K Scientific Ltd. (Beijing, China). Rutin and gallic acid were purchased from Aladdin-Reagent (Shanghai, China). Luteolin (1), quercetin (2), 3-methoxyquercetin (3), ophioglonol (4), ophioglonol 4'-O-α-D-glucopyranoside (5), and pedunculosumoside B (6) used in the present study were isolated from O. thermale.14 The water (resistivity ≥ 18.25 MΩ cm) used was purified with a purity water system (Chengdu, China). All other chemicals used were of analytical grade. Plant materialThe herbs of O. thermale were collected from Wenshan, Yunnan, China, in February 2014, and were identified by Assistant Professor Shu-Da Yang from School of Pharmacy, Kunming Medical University, Kunming, China. A voucher specimen (2014-0t-01) has been deposited in School of Chemical Science and Technology, Yunnan University, Kunming, China. Microorganisms and fermentationAll strains including T. purpurog...