Indole Alkaloids and Chromones from the Stem Bark of Cassia alata and Their Antiviral Activities

Abstract

The Cassia (Leguminosae) genus has attracted a lot of attention as a prolific source of alkaloids and chromones with diverse structures and biological properties. The aim of this study is to screen the antiviral compounds from Cassia alata. The extract of the stem bark of this plant was separated using silica gel, MCI, ODS C18, and Sephadex LH-20 column chromatography, as well as semi-preparative HPLC. As a result, three new indole alkaloids, alataindoleins A–C (1–3); one new chromone, alatachromone A (4); and a new dimeric chromone-indole alkaloid, alataindolein D (5) were isolated. Their structures were determined by means of HRESIMS and extensive 1D and 2D NMR spectroscopic studies. Interestingly, alataindolein D (5) represents a new type of dimeric alkaloid with an unusual N-2−C-16’ linkage, which is biogenetically derived from a chromone and an indole alkaloid via an intermolecular nucleophilic substitution reaction. Compounds 1–5 were tested for their anti-tobacco mosaic virus (TMV) and anti-rotavirus activities, and the results showed that compounds 2–4 showed high anti-TMV activities with inhibition rates of 44.4%, 66.5%, and 52.3%, respectively. These rates were higher than those of the positive control (with inhibition rate of 32.8%). Compounds 1 and 5 also showed potential anti-TMV activities with inhibition rates of 26.5% and 31.8%, respectively. In addition, compounds 1–5 exhibited potential anti-rotavirus activities with therapeutic index (TI) values in the range of 9.75~15.3. The successful isolation and structure identification of the above new compounds provided materials for the screening of antivirus drugs, and contributed to the development and utilization of C. alata.

Biological and Medicinal Properties of Natural Chromones and Chromanones

“…As a result, one new chromone, alatachromone A (62, Figure 10) and a new dimeric chromone-indole alkaloid, alataindolein D (63, Figure 10), were isolated and their structures were determined using HR-ESI-MS and extensive 1D and 2D NMR spectroscopic studies. 47 Compounds 62 and 63 were tested for their anti-TMV and antirotavirus activities, and the results showed 10) and five already described chromones from the whole plants of C. rotundifolia. They were identified as 2-acetyl-5-isopropyl-7methyl-4H-chromen-4-one (64) and 2-acetyl-7-(hydroxymethyl)-5-isopropyl-4H-chromen-4-one (65).…”

“…As a result, one new chromone, alatachromone A ( 62 , Figure 10 ) and a new dimeric chromone-indole alkaloid, alataindolein D ( 63 , Figure 10 ), were isolated and their structures were determined using HR-ESI-MS and extensive 1D and 2D NMR spectroscopic studies. 47 Compounds 62 and 63 were tested for their anti-TMV and antirotavirus activities, and the results showed relevant anti-TMV activities with inhibition rates of 52.3%, and 31.8%, respectively (inhibition rate of the positive control ningnanmycin: 32.8%). Moreover, both compounds exhibited potential antirotavirus activities with TI values of 12.4 and 12.0 (positive control ribavirin: 21.2).…”