Bioactive alkaloids isolated from Waltheria indica (Malvaceae)

Waltheria indica is a plant specie which belongs to Malvaceae family, occurring in the Americas (including Mexico and Brazil), as well as in West Africa, Southeast Asia, and Australia. In Brazil, this species is widely used in traditional medicine as an anti-fungal, anti-inflammatory agent, as well as for the treatment of bronchitis, laryngitis and central nervous system disorders (Cretton et al., 2014). The Waltheria and Melochia genera of the Hermannieae tribe (family Malvaceae) are the most studied under phytochemistry point of view, beeing related to species that genera a new class of quinolin-4-one alkaloids, such as the cyclised and open chained waltheriones (Hoelzel et. al., 2005; Cretton et al., 2014; Cretton et al., 2016). This new class of 4-quinolinone alkaloids have been researched due to a variety of biological activities performed by this class of compounds, such as antifungal and anti-trypanocidal agents, acetylcholinesterase inhibitors and potential anti-HIV activity (Cretton et al., 2014; Cretton et al., 2016; Lima et al., 2009). The dryed and ground branches and stems of a Waltheria indica species collected in the municipality of Piripá (Bahia) were subjected to extraction and extensive maceration with ethanol to provide the crude ethanolic extract (WIFE). This extract was suspended in water/ methanol (3:1) and then partitioned with hexane (WIFH phase), dichloromethane (WIFD phase) and ethyl acetate (WIFAE). As the WIFH and WIFD phases were subjected to successive chromatographic processes of use, mainly silica gel column chromatography, it was possible to isolate the bioactive alkaloids waltherione A, waltherione B and waltherione C. The crude ethanolic extractor and the hexanic, ethyl acetate and dichloromethane phases were tested for fungicidal activities, the last positive result being against a strain showing a CaMDR1 transporter of Candida albicans fungus that is using resistance to fluconazole. This work has great chemosystematic significance, since the waltheriones had been found in both Waltheria and Melochia genera and indicates that W. indica is a potencial source of potential new waltherione analogues.