Nine new ent-labdane-type diterpenoids (1 -9), mostly in the form of the corresponding 16,15-lactones, were isolated from the 85%-EtOH extract of the aerial parts of Andrographis paniculata NEES., together with nine known compounds (10 -18). Their structures were deduced by in-depth NMR spectroscopy and high-resolution mass spectrometry.
Introduction. -Andrographis paniculata NEES. (Acanthaceae) is an erect herb widely distributed in Southeast China. The whole plant is used extensively as an antiinflammatory and antipyretic drug for the treatment of fever, cold, laryngitis, diarrhea, and inflammation [1]. The extract of A. paniculata and its major ent-labdane diterpenoids have been shown to display antiviral [2], bacteriostatic [3], immunostimulatory [4], as well as hepatoprotective and hepatostimulating [5] activities. Phytochemical studies on the aerial parts of A. paniculata have led to the isolation of, so far, more than 20 ent-labdane diterpenoids [6 -13].
As a part of our ongoing research on the metabolism of A. paniculata, we have previously investigated the in vivo metabolism of andrographolide after oral administration in rats and humans [14 -16]. To further explore the in vivo absorbed chemical constituents of the extract of this plant, we decided to systematically investigate the chemical constituents of the 85%-EtOH extract of the aerial parts of A. paniculata, which led to the isolation of nine new ent-labdane diterpenoid lactones or derivatives thereof: 19hydroxy-3-oxo-ent-labda-8(17),11,13-trien-16,15-olide (1), 3,18,19-trihydroxy-entlabda-8(17),13-dien-16,15-olide (2), 3,19-dihydroxy-ent-labda-8(17),12-dien-16,15olide (3), 19-[(b-D-glucopyranosyl)oxy]-19-oxo-ent-labda-8(17), 13-dien-16,15-olide (4), 3,19-dihydroxy-15-methoxy-ent-labda-8(17),11,13-trien-16,15-olide (5), ent-labda-8(17),13-diene-15,16,19-triol (6), 3,15,19-trihydroxy-ent-labda-8(17),13-dien-16-oic acid (7), 3,19-dihydroxy-14,15,16-trinor-ent-labda-8(17),11-dien-13-oic acid (8), and 13,14,15,16-tetranor-ent-labd-8(17)-ene-3,12,19-triol (9). Also isolated were nine known constituents, which could be identified by comparison of their physico-chemical and spectroscopic properties with published data: neoandrographolide (10) [7] [10] [12], 3,14-dideoxyandrographolide (11) [10] [12], andro-