Loratadine, is a non sedating anti histaminic drug used to treat chronic urticaria and allergic rhinitis. Loratadine is metabolised into an active metabolite desloratadine in mammals by CYP450 3A4 and CYP450 2D6 enzymes. Microorganisms have proficiency to imitate the biotransformation reactions that happen in mammals. In preliminary microbial screening process, out of six fungi, two Cunnighmella fungi and one Aspergillus fungus proved the ability to biotransform the loratadine. Then the study was conducted to find the effect of incubation period and substrate concentration on the capacity of fungal biotransformation of loratadine. Different concentrations of substrate i.e, 10 to 60 µg and different incubation periods 18 hrs, 36hrs, 48hrs, 56 hrs, 64 hrs and 72 hrs were selected for study, during incubation for estimation of extent of biotransformation of loratadine by selected three fungi along with their controls. Then these samples were extracted for loratadine metabolite using Diethyl ether: Dichloromethane (70:30) and analysed by HPLC to find the quantity of loratadine metabolite formed under different selected incubation periods and substrate concentrations. The percentage of metabolite formed was calculated using area of respective peaks found in the HPLC chromatograms. Percentage metabolite formed was increased with increase in the substrate concentration in case of Cunnighmella elegans and Cunnighmella echinulata, whereas, in case of Aspergillus niger, it was increased up to 40 µg of substrate concentraton after that a decrease in metabolite formation was found. Maximum amount of metabolite was formed at 64 hrs of incubation in case of all three fungi and further there was no change in the percentage metabolite formed with increase in the incubation time up to 72 hours. Hence, from the above results, it can be concluded that the substrate (loratadine) has shown substrate inhibition when incubated with Aspergillus niger during loratadine biotransformation, It was also found that the process of biotransformation was ceased after 64 hours of incubation period, might be due to exhaustion of nutrients available in the media for their growth and further biotransformation.
