molecules Review Naturally Occurring Calanolides: Occurrence, Biosynthesis, and Pharmacological Properties Including Therapeutic Potential Lutfun Nahar 1,*, Anupam Das Talukdar 2, Deepa Nath 3, Sushmita Nath 4, Aman Mehan 5 , Fyaz M. D. Ismail 4 and Satyajit D. Sarker 4,* 1 Laboratory of Growth Regulators, Institute of Experimental Botany ASCR & Palacký University, Šlechtitel ˚u27, 78371 Olomouc, Czech Republic 2 Department of Life Science and Bioinformatics, Assam University, Silchar, Assam 788011, India;
[email protected] 3 Department of Botany, Gurucharan College, Silchar, Assam 788004, India;
[email protected] 4 Centre for Natural Products Discovery, School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, James Parsons Building, Byrom Street, Liverpool L3 3AF, UK;
[email protected] (S.N.);
[email protected] (F.M.D.) 5 School of Clinical Medicine, University of Cambridge, Cambridge CB2 OSP, UK;
[email protected] * Correspondence:
[email protected] (L.N.);
[email protected] (S.D.S.) Academic Editors: Maria João Matos and Pascal Richomme Received: 30 September 2020; Accepted: 26 October 2020; Published: 28 October 2020 Abstract: Calanolides are tetracyclic 4-substituted dipyranocoumarins. Calanolide A, isolated from the leaves and twigs of Calophyllum lanigerum var. austrocoriaceum (Whitmore) P. F. Stevens, is the first member of this group of compounds with anti-HIV-1 activity mediated by reverse transcriptase inhibition. Calanolides are classified pharmacologically as non-nucleoside reverse transcriptase inhibitors (NNRTI). There are at least 15 naturally occurring calanolides distributed mainly within the genus Calophyllum, but some of them are also present in the genus Clausena. Besides significant anti-HIV properties, which have been exploited towards potential development of new NNRTIs for anti-HIV therapy, calanolides have also been found to possess anticancer, antimicrobial and antiparasitic potential.