**2. Phytochemical investigations of** *A. paniculata*

The characteristic secondary metabolites encountered in *A. paniculata* have considerably enhanced its importance in the arena of medicinal plants. It is specifically rated high in therapeutic action in curing liver disorders, common cough and colds in human (Niranjan *et al*., 2010). *A. paniculata* chiefly contains diterpenes, lactones, and flavonoids. Flavonoids mainly exist in the root, but have also been isolated from the leaves. The aerial parts contain alkanes, ketones, and aldehydes. Although it was initially thought that the bitter substance in the leaves was the lactone andrographolide, later investigations revealed that the leaves contained two bitter principles-andrographolide and a compound named kalmeghin. Four lactoneschuanxinlian A (deoxyandrographolide), B (andrographolide), C (neoandrographolide) and D (14-deoxy-11,12-didehydroandrographolide)-were isolated from the aerial parts in China (Chang and But, 1987). A diterpene glucoside (deoxyandrographolide-19-β-D-glucoside) has been detected in the leaves (Weiming *et al*., 1982) and six diterpenoids of the ent-labdane type, two diterpene glucosides and four diterpene dimers (bis-andrographolides A, B, C, and D) have been isolated from aerial parts (Matsuda *et al*., 1994). Two flavonoids identified as 5,7,2',3' tetramethoxyflavanone and 5-hydroxy-7,2',3'-trimethoxyflavone were isolated from the whole plant (Koteswara *et al*., 2004), while 12 new flavonoids and 14 diterpenoids have been reported from the aerial parts (Chen *et al*., 2006a, 2006b). Two new flavonoid glycosides and a new diterpenoid (andrographic acid) were recently reported (Li *et al*., 2007), and two new entlabdane diterpenoid glycosides were also isolated from the aerial parts of *A. paniculata* (Zhou *et al*., 2008).
