Indian Journal of Traditional Knowledge Vol. 16 (2), April 2017, pp. 189-196 In vitro biological effects of Crataegus microphylla C. Koch P Aksoy-Sagirli 1 , T Yilmaz-Ozden 1 , N Ozsoy 1 , B Ozbek Celik 2 , S Kultur 3 & G Melikoglu 4* 1 Department of Biochemistry, Faculty of Pharmacy, Istanbul University, 34116 Istanbul, Turkey; 2 Department of Pharmaceutical Microbiology, Faculty of Pharmacy, Istanbul University, 34116 Istanbul, Turkey; 3 Department of Pharmaceutical Botany, Faculty of Pharmacy, Istanbul University, 34116 Istanbul, Turkey; 4 Department of Pharmacognosy, Faculty of Pharmacy, Istanbul University, 34116 Istanbul, Turkey E-mails: gulaymelikoglu@hotmail.com*, aksoyp@istanbul.edu.tr, bernaozbek@hotmail.com, sukrankultur@hotmail.com, tugbayilmazz@hotmail.com, nozsoy@istanbul.edu.tr Received 25April 2016, revised 28 October 2016 Cratageus species are rich in phenols and flavonoids, which are active compounds that possess beneficial effects. This study aimed to identify the antioxidant, antimicrobial, DNA damage protection activities, and the capacities of acetylcholinesterase (AChE), thioredoxin reductase (ThxR), and -glucosidase inhibition of the methanol extract of Cratageus microphylla. The plant extract inhibited the formation of free radicals in various assay systems, such as 2,-2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,2'-diphenyl-1-picrylhydrazyl (DPPH), lipid peroxidation (anti-LPO) and ferric reducing antioxidant power (FRAP) assays. According to the findings, the extract inhibited the lipid peroxidation and neutralized stable DPPH, and ABTS cation radicals with EC 50 values of 0.766 ± 0.026 mg/mL, 0.207 ± 0.009 mg/mLand 0.756 ± 0.048 mg/mL, respectively. The extract also acted as a reductant as indicated by the FRAP value (2.841 ± 0.096 mM Fe 2+ ), thus exhibiting its potential as an antioxidant. Moderate AChE (4.94 ± 0.29 mg/mL) and -glucosidase (14.41 ± 0.29 mg/mL) and significant ThxR (EC 50 = 0.61 ± 0.06 mg/mL) inhibition activities were observed. DNA damage formation in in vitro assays was 51 % at 0.78 μg/mL concentrations. Therefore, C. microphylla can be considered as a good source of antioxidant, antimicrobial, antidiabetic, anticholinesterase, and anticancer agents. Keywords: Cratageus microphylla, Antioxidant, Anti-acetylcholinesterase, Thioredoxin reductase inhibition, -glucosidase inhibition, DNA damage protection IPC Int. Cl. 8 : A36K 36/00, C09K 15/00, C12P, C12N, C12M, A01D 4/04 The Crataegus L. (Rosaceae) species known as “Hawthorn” has been used traditionally since ancient times. The leaves and flowers, and sometimes the fruits, of the plant have been used in folk medicine. Studies have shown that this species especially affects the cardiovascular system 1-3 . Crataegus extracts exhibit a positive inotropic effect. They play an important role in the activation of heart muscle cells and coronary dilatation, and they regulate blood flow 4 . Moreover, aside from having a regulator effect in the cardiovascular system as mentioned above, the Crateagus species also has free radical scavenging and anti-lipoperoxidant activities 5,6 . The Crataegus species is generally rich in proanthocyanidins, fenols, and flavonoids which are responsible for the most of its biological activities 7 . Crataegus microphylla C. Koch is one of the 26 species of Crataegus that grows in Turkey 8-10 . A total of nine flavonoids were isolated from its flowers and leaves. According to the results of the quantification, flavonoid content of 2.04 % in the leaves and 1.28 % in the flowers of C. microphylla were found. These results are comparatively high for the Crataegus species as 0.7 % is the minimal flavonoid content of leaves and flowers 11 . In another study, the results indicated that the methanol extract of C. microphylla preserved endothelium-dependent vascular relaxation and contractions in diabetes induced by streptozotocin 12 . Hosseinimehr et al. 13 reported that C. microphylla had 2, 2' – diphenyl – 1 - picrylhydrazyl (DPPH) scavenging activity. However, no information was available on its other biological activities. Therefore, this study aimed to determine the DNA protective effect and the antioxidant and antimicrobial activities of C. microphylla extract and to identify its potential inhibitory effects on thioredoxin reductase (TrxR), acetylcholinesterase (AChE), and -glucosidase enzymes. ___________ *Corresponding author