Lippia species share
various pharmacological activities
and are used in traditional cooking and medicine worldwide. Combined
chromatographic techniques such as column chromatography, high-performance
liquid chromatography, and countercurrent chromatography led to the
purification of two new antifungal phenylpropanoid glycosides, lippiarubelloside
A (1) and lippiarubelloside B (2), by bioactivity-directed
fractionation of an ethanol-soluble extract from Lippia rubella, in addition to the known active related compounds forsythoside
A (3), verbascoside (4), isoverbascoside
(5), and poliumoside (6). The structures
of compounds 1 and 2 were determined by
comparison of their NMR spectroscopic data with the prototype active
compound 4. Cryptococcus neoformans,
which causes opportunistic lung infections, was sensitive to compounds 1–6 in the concentration range of 15–125
μg/mL. A synergistic effect (FICindex = 0.5) between 3 and amphotericin B was demonstrated. The glycosylated flavonoids
pectolinarin (7), linarin (8), and siparunoside
(9) were also isolated.
Cytotoxic 6-heptyl-5,6-dihydro-2H-pyran-2-ones
are chemical markers of Hyptis (Lamiaceae) and are
responsible for some of the therapeutic properties of species with
relevance to traditional medicine. The present investigation describes
the isolation of known pectinolides A–C (1–3), in addition to the new pectinolides I–M (4–8), from two Mexican collections of H. pectinata by HPLC. The novel biosynthetically related
monticolides A (9) and B (10) were also
isolated by high-speed countercurrent chromatography from H. monticola, an endemic species of the Brazilian southeastern
high-altitude regions. A combination of chemical correlations, chiroptical
measurements, and Mosher ester NMR analysis was used to confirm their
absolute configuration. The utility of DFT-NMR chemical shifts and J
H–H calculations was assessed for epimer
differentiation. Molecular docking studies indicated that 6-heptyl-5,6-dihydro-2H-pyran-2-ones have a high affinity for the pironetin-binding
site of α-tubulin, which may be a possible mechanism contributing
to the cytotoxic potential of these small and flexible molecules.
T he structure of lippiarubelloside B (2) was drawn incorrectly in the original paper. The chemical shifts for rhamnose H-3″ and H-4″ were inverted. The chemical shifts and coupling constants used for spectroscopic simulation to conclusively duplicate the registered 1 H NMR data and thus permit the correct chemical shift assignments and coupling constants of all overlaid signals and tightly coupled protons in compound 2 (Table 2) are rhamnose H-3″ δ 3.77 (1H dd, 9.3, 3.3) and rhamnose H-4″ δ 4.96 (1H dd, 9.3, 9.3). Therefore, the structure graphic for compound 2 should be replaced by the one below. The authors sincerely apologize to the scientific community for the inconvenience caused by this error.Corrected structure of lippiarubelloside B (2):
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