Anthraquinones from the Roots of Knoxia valerianoides

Abstract

To investigate the chemical constituents of the roots of Knoxia valerianoides and their biological activities. The anthraquinones were isolated by using a combination of various chromatographic techniques including column chromatography over silica gel, Sephadex LH-20, and reversed-phase HPLC. Structures of the isolates were identified by their physical-chemical properties and spectroscopic analysis including 2D NMR and MS. Antioxidant, anti-HIV, neuroprotective, and cytotoxic activities were screened by using cell-based models. Twenty-two constituents were isolated from an ethanolic extract of the roots of K. valerianoides. Their structures were identified as nordamnacanthal (1), ibericin (2), rubiadin (3), damnacanthol (4), 2-ethoxymethylknoxiavaledin (5), 3-hydroxymorindone (6), knoxiadin (7), 2-formyl knoxiavaledin (8), lucidin (9), xanthopurpurin (10), 1, 3-dihydroxy-2-methoxy-9, 10- anthraquinone (11), lucidin(-methyl ether (12), digiferruginol (13), 3-hydroxy-2-methyl-9,10-anthraquinone (14), rubiadin-1-methyl ether (15), 6-methoxylucidin (-ethyl ether (16), 1,3,6-trihydroxy-2-methyl-9,10-anthraquinone (17), 1,3-dihydroxy-2-hydroxy methyl-6-methoxy-9,10-anthraquinone (18), 1,3,6-trihydroxy-2-methoxymethyl-9,10- anthraquinone (19), 3,6-dihydroxy-2- hydroxymethyl-9,10-anthraquinone (20), and 1,6-dihydroxy-2-methyl-9,10-anthra quinone (21). In the in vitro assays, at a concentration of 1 x 10(-5) mol x L(-1), no compounds were active against human cancer cell lines (HCT-8, Bel7402, BGC-823, A549, and A2780), deserum and glutamate induced PC12-syn cell damage, LPS induced NO production in macrophage, Fe2+-cystine induced rat liver microsomal lipid peroxidation, HIV-1 replication, and protein tyrosine phosphatase 1B (PTP1B). Compounds 9-21 were obtained from the roots of K. valerianoides for the first time.