ISSN 2409-4943. Ukr. Biochem. J., 2020, Vol. 92, N 6 143 © 2020 Lootsik M. et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. UDC 577.114.083:579.6:638.178 HONEYBEE CHITOSAN-MELANIN COMPLEX: ISOLATION AND INVESTIGATION OF ANTIMICROBIAL ACTIVITY M. LOOTSIK 1 , N. MANKO 1 , O. GROMYKO 2 , S. TISTECHOK 2 , M. LUTSYK (Jr.) 3 , R. STOIKA 1 1 Institute of Cell Biology, National Academy of Sciences of Ukraine, Lviv; 2 Ivan Franko National University of Lviv, Ukraine; 3 Danylo Halytsky Lviv National Medical University, Ukraine;  e-mail: stoika.rostyslav@gmail.com Received: 4 May 2020; Accepted: 13 November 2020 Antimicrobial activity of marine crustaceans chitosans is well studied and is widely used in medicine, while chitosans of insects are poorly investigated in this aspect, though they might also be of practical signif- cance. The aim of this study was to isolate and purify chitosan-melanin complex (CMC) from the honeybee corpses and to estimate its antimicrobial activity. Antibacterial activity of CMC was evaluated by MTT test, antifungal activity towards Candida albicans was estimated by calculating colony forming units (CFU meth- od). The modifed method of CMC isolation and purifcation was described which difers from the known analogs in deacetylation of chitin-melanin complex by its hydrolysis in 40% NaOH without previous melanin elimination and in further purifcation of CMC by diferential solubilization at distinct pH values. The anti- microbial activity of CMC was characterized by prevalence of candidacidal efect, IC 50 towards laboratory strain of C. albicans was 50 μg/ml. The ranking of studied bacteria sensitivity to the CMC action decreased as: E. coli > St. aureus > Ps. aeruginosa. It is suggested that CMC isolated from the honeybee corpses might be a perspective constituent of medicinal compositions for treatment of lesions caused by C. albicans infection. K e y w o r d s : chitosan-melanin complex, honeybee corpses, MTT test, antimicrobial activity. T he antimicrobial activity of chitosan and its derivatives obtained from marine crusta- ceans is well investigated and documented [1,2]. This property of chitosan is widely used in dressing materials for healing wounds and burns [3], the comprehensive information up to 2011 year see in excellent review by Dai T. et al. [2]. Further in- vestigations were devoted to an enhancement of the antimicrobial activity of chitosan or its fragments by their complexation with diferent antimicrobial agents, including nanoparticles, and via an improve- ment of water solubility of their preparations in neu- tral or weak alkaline media [4-8]. Biological, specifcally the antimicrobial ac- tivity of chitosan isolated from the honeybee (Apis mellifera), is much less investigated, compared to chitosans obtained from marine crustaceans though it might also have a practical signifcance [9, 10]. The available publications devoted to isolation and purifcation of chitin/chitosan from insect sources were addressed mainly to investigation of physico- chemical properties of the obtained products [9-13]. The information on the biological efects of the honeybee chitosan and chitosan-melanin complex (CMC) is rather scarce [14-16]. It was shown that CMC from the honeybees efectively absorbs water- soluble compounds of the radionuclides 90 Sr and 233 U from their solutions [14]. A method of isolation the CMC from the honeybee corpses and a description of its application as a dietary supplement in fattening of calves were provided in the patent of the Russian Federation [10]. Paper devoted to preparation of chi- tosan from the honeybees (entitled Beetosan R ) and to the biological efects of the hydrogels combined with the bioactive compounds of plant origin have been published [17]. The formation of complex with melanin in in- sect cuticle is a characteristic property of the hon- doi: https://doi.org/10.15407/ubj92.06.143