Plants are the natural resources for variousenzymatic as well as enzyme inhibitory activities. Some animal studies havesuggested the role of plant extracts in preventing an excessive postprandialrise of blood glucose levels (Karau et al.,2012). The use of antioxidants along with carbohydrate-degradation inhibitingcompounds has been widely reported to reducing the levels of oxidative stressand in slowing or preventing the development of complications associated withchronic diseases (Oyenihi et al.,2015; Zhang et al., 2015).
In thepresent study, the strain J-7, isolatedfrom the root tissues Syzygium cumini, was presumptively identified tobe belonging to Streptomycessp. The ethyl acetate extract of endophytic actinobacterium strain was thustested for different in vitro starchdegradation inhibition and antioxidant properties. The ethyl acetate extract ofJ-7 effectively controlled ?-amylase and ?-glucosidase based reactions. Likewise,J-7 extract was able to inhibit DPPH free radicals in vitro. The method is based on the conversion of DPPH freeradical in the presence of a hydrogen-donating antioxidant to a non-radical formby the reaction (Christhudaset al.
, 2013).Hydroxyl radical scavenging capacity of a compound is directly related to itsantioxidant activity (Shukla et al.,2009). Ethyl acetate extract of J-7 prevented the free radical-mediateddeoxyribose damage by reacting with hydroxyl freeradicals. In the ?-carotene linoleate model system, coupled oxidation of?-carotene and linoleic acid takes place, which generates free radicals.
As aresult, the system loses its chromophore and characteristic orange color isproduced, which can be monitored spectrophotometrically (Christhudas et al., 2013). In ourstudy, the inhibition of ?-carotene bleaching by J-7 extract showed almostequivalent activity with vitamin C (500 ?g/ml).For measurement of reductive ability, the conversion of Fe3+ to Fe2+in the presence of extract was investigated. The reducing power increased withincreasing concentration of the extract and was found to be higher as comparedto BHT. The reducing capacity of a compound may be an indicator of itspotential antioxidant activity (Meir etal., 1995).
Competitive inhibitionrefers to that mode in which substrate affinity of the enzyme is hindered bythe presence of another molecule with similar symmetry but higher affinitytowards the enzyme. The results of present study indicated that the extractexhibited competitive modes of inhibition towards both the enzymes tested. Thus,it may be assumed that providing doses of extract in vivo at regular intervals will result in decreased exposure ofthe enzyme to the carbohydrate moiety resulting in suppression of secondaryeffects of diabetes.The antidiabetic, antioxidantand scavenging are believed to be due to the presence of measurable amount of phenolicsas estimated by Folin-Ciocalteau method (Moradi-Afrapoli et al., 2012). Polyphenols obtained from plants have beendemonstrated to have significant antioxidant activity. This activity isbelieved to be mainly due to their redox properties which play an importantrole in adsorbing and neutralizing free radicals, quenching singlet and tripletoxygen, or decomposing peroxides (Upadhyay etal.
, 2010). Our assumptions arefurther supported by the results of LC-MS analysis, which indicated theoccurrence of chromene family of compounds. Chromenes have been widelydemonstrated to exhibit a remarkable array of biochemical and pharmacologicalactivities. They constitute the basic structural back bone of many types oftannin and polyphenols widely present in plants e.
g. green tea, fruits andvegetables (Rensburg et al., 1997).The presence of the chromene-containing structure has been associated with thecapability to prevent several diseases (Kennedy and Thornes, 1997). Syntheticanalogues have attracted considerable attention due to their useful biologicaland pharmacological properties including antimicrobial (El-Saghier et al., 2007; Kumar et al.
, 2009), antioxidant (Alvey et al., 2008), anticancer (Kemnitzer et al., 2008), anticoagulant,antidiabetic (Vishnu et al., 2015),hypotensive (Tandon et al., 1991),local anesthetic (Longobardi et al.,1990) and central nervous system activities as well as treatment of Alzheimer’sdisease (Bruhlmann et al., 2001) andSchizophrenia disorder (Kesten et al.
,1999). Substances, like hydroxyl-coumarins (Hoult and Paya, 1996), directlyrecombine free radicals and interrupt the initiation and/or propagation of theinduced chain reactions. Due to the typical phenolic behavior (Traykova andKostova, 2005) they act as potent metal chelators and free radical scavengers,resulting in a powerful antioxidant effect. To show antioxidantactivity, a coumarin derivative has to possess at least one hydroxyl group (Shukla et al., 2009). The evaluation of coumarin isolates from Geraniumwallichianum (Ismail et al.
, 2009) and Korean medicinalplants (Tandon et al., 1991)highlights the presence of catechol moiety and oxygen containing scaffold inC-6 and C-7 positions of the coumarin core for antioxidant activity. Also, the?-pyrone coumarin ring uplifts free radical scavenging activity, antilipidperoxidation ability and also has a suppressive effect on enzymes (Tandon et al., 1991). Synthetic compounds,4-methylcoumarins (Cavar et al.,2009), substituted 7- or 8-hydroxybenzof-coumarins,6-hydroxybenzoh-coumarins and 7-azomethinecoumarins were tested for theirantioxidant ability in vitro (Kontogiorgisand Hadjipavlou-Litina, 2004)and for their ability to interact with DPPH stable free radical (Al-Amiery etal., 2015 a), scavenging of hydrogen peroxide (Al-Amiery etal., 2015 b), superoxide anion and inhibition of lipid peroxidation,too (Verma et al., 2014).