Antiviral sesquiterpenes from leaves of Nicotiana tabacum
Three unreported sesquiterpenes possessing two new skeletons, tabasesquiterpenes A–C (1–3), together with
three known sesquiterpenes (3–6) were isolated from the leaves of Nicotiana tabacum. Their structures were determined
mainly by spectroscopic methods, including extensive 1D- and 2D-NMR techniques. Compounds 1–6
were evaluated for their anti-tobacco mosaic virus (anti-TMV) activities. The results showed that compound 2
exhibited high anti-TMV activity with inhibition rate of 35.2%, which were higher than that of positive control
(ningnanmycin). The other compounds also showed potential anti-TMV activity with inhibition rates in the
range of 20.5–28.6%.
Nicotiana tabacum, tobacco, is a stout herbaceous plant in the
Solanaceae (nightshade family) that originated in the tropical
Americas (South America, Mexico, and the West Indies) and now cultivated
worldwide as the primary commercial source of tobacco, which
is smoked or chewed as a drug for its mild stimulant effects [1–2].
N. tabacum is a kind of plant containing most complex secondary
metabolites in nature. It was reported that more than 2549 kinds of
chemical compositions have been identified in N. tabacum, while up to
8700 kinds of chemical compositions were found in tobacco and tobacco
substitutes and cigarette smoke (including combustion products) [3].
Our previous investigation of this species led to the discovery of a
number of new compounds that showed various bioactivities, such as
anti-HIV-1, anti-TMV, and cytotoxicity by our groups [4–9]. In continuing
efforts to utilize N. tabacum and identify bioactive natural products,
the phytochemistry investigation of the leaves of Yunyan 201 (a variety
of N. tabacum) led to the isolation of three new (1–3) and three known
(4–6) sesquiterpenes, of which possessed two unprecedented skeletons
(one skeleton for compounds 1 and 2 while the other for compound 3).
This paper deals with the isolation, structural elucidation, and anti-TMV
activity of these compounds.