Aqueous fraction of Sapindus rarak D.C. fruit extract mediated one-pot three component construction of 9,9-dimethyl-12-phenyl-9,10-dihydro-8H-benzo[a]xanthen-11(12H)-one

In this study, we report 3-component combination of 2-naphthol, dimedone and benzaldehyde in 9,9-dimethyl-12-phenyl-9,10-dihydro-8H-benzo[a]xanthen-11(12)-one synthesis using water fraction of Sapindus rarak D.C. fruit extract. This extract promoted an efficient synthesis under mild reaction conditions. The compound structure was confirmed by FT-IR and Mass analysis.

In recent years, role of green chemical-based catalysts has grown tremendously. The highlighted aspect of green chemistry is reduction in the use of harmful chemical reagents [10]. Using plant or its part as a potential biocatalyst in the synthesis of organic compounds is one of the efforts that have been conducted. Organic synthesis using natural materials generates less waste than the conventional methods [11].
Sapindus rarak D.C. is a plant used as a traditional detergent. The fruits, roots, and seeds contain triterpenoids, some polyphenols and saponins that act as anti-cancer, anti-bacterial, and antiinsecticides. The content of saponin content in Sapindus rarak D.C. fruit reaches 10-11.5 % [12]. Saponins are group of glycoside compounds that serve as a washing agent that has properties such as soap and acts as a surfactant. Surfactants are best known to dissolve the non-polar materials. That ability has established the aqueous surfactant systems to be notably popular option for organic solvents [13] or stabilizing and capping agent in nanoparticles syntheses [14]. Therefore, with interesting properties of aqueous extract of Sapindus rarak D.C. fruit, we investigate its performance as an ecofriendly acidic surfactant type for the synthesis of 9,9-dimethyl-12-phenyl-9,10-dihydro-8Hbenzo[a]xanthen-11(12H)-one (figure 1).

General
All chemicals required were obtained from Merck and used without further purified. Sapindus rarak

Preparation of Sapindus rarak D.C. fruit extract
Preparation of Sapindus rarak D.C. fruit extract (SRDFE) was carried out by maceration method. Sapindus rarak D.C. (50 g) dry powder was macerated in methanol (1:5 w/v) for 2 days. The extract was filtered and then centrifuged for 10 min. The filtrate was evaporated using a rotatory evaporator. Furthermore, this crude extract was separated by deionized water and hexane by a ratio of 1:1 (v / v). These fractions were phytochemically screened to determine secondary metabolites content such as saponins, alkaloids (Wagner test), flavonoids, steroids, terpenoids (Salkowski test), and tannins [15]. Further, aqueous fraction will be used to mediate multicomponent synthesis of a benzoxanthene derivative.

Results and discussion
The phytochemical screening of water and n-hexane fraction of Sapindus rarak D.C. fruit extracts revealed the presence of several secondary metabolites. Saponins were strongly observed in water fraction but not in n-hexane fraction. Alkaloids were found only in n-hexane fraction. Meanwhile, terpenoids were detected in both fractions. The results are summarized in table 1.
FT-IR spectrum of aqueous fraction of Sapindus rarak D.C. fruit extract (figure 2) showed peak at 1730 cm -1 due to carbonyl stretching vibration. A broad peak at 3353 cm -1 is associated to O-H vibration. Furthermore, peaks at 2933 and 1613 cm -1 are ascribed to the C-H sp 3 and C=C vibrations, respectively. All those peaks may be attributable to the presence of saponins in the extract [16].

Conclusions
We successfully synthesized 9,9-dimethyl-12-phenyl-9,10-dihydro-8H-benzo[a]xanthen-11(12H)-one using aqueous extract of Sapindus rarak D.C. fruit extract containing saponins. The optimum conditions of the synthesis were obtained when 5 mL of extract used at 100 ºC for 20 min. The present research highlighted an easy work-up, low-cost, efficient and eco-friendly manner in the synthesis of biologically potent natural product derivative with excellent yield.