RESEARCH ARTICLES CURRENT SCIENCE, VOL. 118, NO. 6, 25 MARCH 2020 931 . Averrhoa bilimbi in organic transformation: a highly efficient and green biosurfactant for the synthesis of multi-functional chromenes and xanthenes Bhagyashree M. Patil 1 , Snehali R. Mali 2 , Bhimrao M. Patil 3 and Suresh S. Patil 2, * 1 Institute of Forensic Science, 15, Madam Cama Road, Mumbai 400 032, India 2 Green Research Laboratory, Department of Chemistry, PDVP College, Tasgaon, District Sangli 416 312, India 3 Institute of Science, 15, Madam Cama Road, Mumbai 400 032, India A simple, clean and efficient one-pot three-component synthesis of multi-functional chromene and xanthene derivatives has been developed in this study in the presence of a catalytic amount of Brǿnsted acidic-type biosurfactant bilimbi fruit extract (BFE) under ele- vated temperature condition. BFE is an unprocessed micellar catalyst that works well in an ethanolic aqueous medium. Employment of ethanol as a co- surfactant enhances catalytic performance of BFE as a biosurfactant. The presence of micelles in the reaction medium was detected using light microscopy and their critical micelle concentration was measured by elec- trical conductivity method. Some new derivatives of chromene and xanthene are reported here. This novel catalytic medium obtained from an environmentally renewable resource is highly advantageous because of its non-toxicity, higher efficiency, operational simpli- city, bio-compatibility as well as absence of any tedious work-up or column chromatography and thus no waste generation. Here, we also signify the ‘green- ness and sustainability’ of the present protocol on the basis of EcoScale metric which validates the practical application of the synthetic procedure. Keywords: Bilimbi fruit extract, biosurfactant, green chemistry, natural catalyst. THE development of a proactive protocol for chemical transformations with high efficacy and reduced environ- mental impact is an important goal in green chemistry and in future sciences. With reduced environmental im- pact, young discipline of chemistry, green chemistry, promotes the use of highly efficient and environmental benign synthetic procedures to deliver life-saving medi- cines, and accelerating the guide optimization processes in drug discovery. In the synthetic organic reactions, sol- vents handle80% of the total mass and also in 70% cases they are just incinerated to recover heat 1,2 . Therefore, their substitution with more environment-friendly options can directly have a positive effect on both emission and hazardous issues 3 . Hence, it is desirable to use environ- mentally benign water as a safe, abundant, inexpensive and non-toxic solvent instead of organic solvents 4 . Due to the same features, accomplishing organic reactions in water has been explored over the past few decades 5–8 . Methods Nowadays, a viable alternative for the development of green protocols are biosynthetic processes utilizing bio- based solvents or catalysts for organic tranformations 9 . The advanced and/or newer organic promoters which per- form well in the aqueous medium will be beneficial in reaction handling, product selection and purification, im- proving the reaction rate, and reducing toxic solvent con- sumption and disposal problems, etc. These are found to be important from the industrial point of view. Hence- forth, there is demand for the use of catalyst/media which works avoiding the hydrophobicity of organic precursors and reagents, which is satisfied by the use of surfactant assembled aqueous micelles. Typically, the micellar envi- ronment has a pronounced effect in enhancing the reac- tion rate with good efficiency exhibiting environmentally benign character, which act as ‘nanoreactors’ characte- rized by exclusive features 10 Hitherto, organic transfor- mations involving surfactants in aqueous media have received considerable attention from researchers 11,12 . All these findings validate the case of a naturally occurring medium/phase acting as surfactant, known as a biosurfactant. The surfactants that are directly obtained from natural sources, viz. plants, animals, or microbial cells, or by separation procedures such as extraction, pre- cipitation or distillation are known as biosurfactants. They have potential industrial applications such as use in *For correspondence. (e-mail: sanyujapatil@yahoo.com) improved oil recovery, lubricants, food processing