Indonesian Journal of Chemical Research http://ojs3.unpatti.ac.id/index.php/ijcr Indo. J. Chem. Res., 9(2), 129-136, 2021 DOI: 10.30598//ijcr.2021.9-bud 129 Study of Molecular Docking of Alkaloid Derivative Compounds from Stem Karamunting (Rhodomyrtus tomentosa)Against α-Glucosidase Enzymes Budi Mulyati 1* , Riong Seulina Panjaitan 2 1 Industrial Engineering, Engineering Faculty, Nurtanio University, Bandung 2 Pharmaceutical science, Pharmacy Faculty, 17 Agustus 1945 University, Jakarta * Corresponding Author: b.mulyati@unnur.ac.id Received: Received in revised: Accepted: Available online: Abstract Karamunting plant (Rhodomyrtus tomentosa) is a traditional medicinal plant. The leaves, roots, stems, and fruits of Karamunting have been identified, and their biological activities are antioxidants, antibacterial, antidiabetic, anti-inflammatory and anticancer that contained alkaloids, tannins, and flavonoids. The types of alkaloids found in karamunting stems are homolycorine, ismine, lycorine, maritidine and tazetine. This study aims to determine the binding score of alkaloid-derived compounds with protein α-glucosidase and determine the protein's active site bound to the ligand. The method used in this research is Protein-Ligand ANT-System (PLANTS). The results showed that the anchoring score of homolycorine was -60.83 kcal/mol, ismine -64.42 kcal/mol, lycorine -71.20 kcal/mol, maritidine -61.82 kcal/mol, and tazetine -65.02 kcal/mol. The active sites used for binding are Glu526, Gly555, and Pro556. The average score for anchoring alkaloid-derived compounds with protein α-glucosidase is 83.84%. This number indicates that karamunting stems can be used as antidiabetic. Keywords: Karamunting, alkaloids, antidiabetic, docking, PLANTS. INTRODUCTION Diabetes Mellitus is one of the non-contagious diseases and is one of the comorbid or accompanying diseases in patients infected with Covid-19. Based on data from the International Diabetes Federation (2020), Indonesia ranks 7th out of 10 countries with the highest number of diabetes patients. There are more than 10.8 million people with diabetes in Indonesia. The prevalence of diabetes mellitus shows an increase with the patient's increasing age, which reaches its peak at the age of 55-64 years (Widiastuti, 2020). Various efforts to prevent and treat diabetes continue to be made, including developing various types of treatment. One of them is to look for new sources of medicine from natural ingredients. Many herbal plants have antidiabetic activity because they have active compounds that play a role, including flavonoids and alkaloid. Treatment of diabetes mellitus can be done medically or traditionally. Medical treatment can be done orally or by injection, namely insulin, but the cost of this treatment is relatively expensive if used continuously. Alternative medicine by taking traditional medicine is an option because it is obtained easily. One of the plants used as traditional medicine by the people of Kalimantan is karamunting (Rhodomyrtus tomentosa). This plant belongs to the Myrtaceae family and has the international name Rosemyrle (Ningrum, Purwanti, & Sukarsono, 2016). Karamuntings’ stem contains flavonoids, alkaloids, saponins, tannins, terpenoids, and phenolics. Alkaloid compounds are effective as anti-diarrhea, anti-diabetic, anti-microbial, and anti-malarial. Still, some alkaloid compounds are toxic, so it is necessary to identify alkaloid compounds whose benefits can be known. Furthermore, Ningrum, Purwanti, & Sukarsono (2016) research showed that the alkaloids found in the karamunting plant were Maritidine, Homolycorine, Ismine, Tazettine, and Lycorine (Ningrum et al., 2016). α-Glucosidase inhibitor is a type of drug for type 2 diabetes that works to block starch metabolism by inhibiting enzymes in the intestine to break down carbohydrates to slow down glucose absorption (Ak, Juliani, Sugito, & Abrar, 2019; Laily & Khoiri, 2016; Ouassou et al., 2018; Yin, Zhang, Feng, Zhang, & Kang, 2014). There are two approaches in computational chemistry, namely molecular mechanics and electron structure theory. Molecular mechanics is an empirical method used to express the potential energy of molecules as a function of geometric variables.