Compound 1 was obtained as an amorphous powder with a
specific rotation of [α]D
25 −17. Its molecular formula,
C20H28O13, was deduced by the 13C NMR data and the
molecular ion [M + Na]+ at m/z 499.1431 (calcd for
C20H28O13Na, 499.1428) in the positive-ion HR-ESIMS. The
IR spectrum showed absorption bands for hydroxy (3398
cm−1) and carbonyl (1707 cm−1) groups and an enol ether
system (1595 cm−1). The 13C NMR spectrum (Table 1)
showed 20 carbon signals including seven in a glucopyranosyl
unit, three carbonyl groups, a methoxy group, and the
remaining nine in the iridoid moiety. The 1H and 13C NMR
data of 1 displayed signals characteristic of an iridoid glycoside,
which were similar to those reported for barlerin (12) isolated
from this plant.12,13 The only difference between 1 and 12 was