Panaxindole, a novel indole alkaloid N-glucoside from the leaves of Panax vietnamensis Ha et Grushv. (Vietnamese ginseng).

Vietnamese ginseng (Panax vietnamensis Ha and Grushv., Araliaceae) is indigenous in the central highlands of Vietnam and the southernmost distribution in the Panax genus. Like other ginseng, Vietnamese ginseng is well known has been used as a tonic and for management of certain diseases in the traditional medicine. Nevertheless, it is noteworthy that in respect to the long history in use and systematic studied on Korean ginseng (P. ginseng), American ginseng (P. quinquefolius), Japanese ginseng (P. japonicus), and Chinese ginseng (P. notoginseng), the up-to-date published database on Vietnamese ginseng is relatively much less extensive. In our ongoing research on the promising Vietnamese medicinal plants, the present phytochemical investigation of the ethanol extract of the leaves of Panax vietnamensis led to the isolation of three compounds (1-3), including a new indole alkaloid N-glycoside (1) and two known compounds. Their structures were elucidated based on extensive physiochemical and chemical methods, especially the interpretation of NMR and MS spectra. The absolute configuration of 1 was determined based on the comparison of its experimental and theoretical ECD spectra along with NMR calculation. Compound 1 is naturally isolated N-glycoside, which is rarely found in natural products. The isolated compounds showed weak or no inhibitory activity against acetylcholinesterase enzyme (AChE).

New oligomeric neolignans from the leaves of Magnolia officinalis var. biloba.

Six new oligomeric neolignans including two trimeric neolignans (1 and 2) and four dimeric neolignans (3-6) were isolated from the leaves of Magnolia officinalis var. biloba. Their structures were determined based on HR-ESIMS and NMR data, as well as electronic circular dichroism (ECD) calculations. Compound 1 is formed from two obovatol moieties directly linked to an aromatic ring of the remaining obovatol moiety, which is an unprecedented type of linkage between monomers. All isolates were assessed for their inhibitory effects on NO production in LPS-stimulated RAW 264.7 macrophage cells. Compounds 1 and 3 showed significantly inhibitory activities with IC50 values of 6.04 and 3.26 µmol·L-1, respectively.

New lignans and acetophenone derivatives with α-glucosidase inhibitory activity from the leaves of Melicope patulinervia.

Four new lignans, patulinones A-D (1-4) and three new acetophenone derivatives, patulinones E-G (5-7) were isolated from the leaves of Melicope patulinervia. Their structures were elucidated on the basis of the interpretation of HR-ESIMS, NMR, CD data. All the isolated compounds were evaluated for α-glucosidase inhibitory activity. Of the isolates, compound 4 was found to exhibit the strongest inhibition against α-glucosidase with IC50 value of 6.02 ± 0.46 µM.

New obovatol trimeric neolignans with NO inhibitory activity from the leaves of Magnolia officinalis var. biloba.

Six new obovatol trimeric neolignans, houpulignans A-F (1-6) were isolated from the leaves of Magnolia officinalis var. biloba. Their structures were determined on the basis of the interpretation of HRESIMS, NMR data, and electronic circular dichroism (ECD) calculations. Compounds 1 and 2 are the first examples of neolignans derived from three units of obovatol bearing a rare 1,4-benzodioxepane moiety. Compound 3 possesses a benzodihydropyran ring, meanwhile three units of obovatol in 4-6 are connected by an alkyl chain. Compounds 1-3 inhibited NO production in LPS-stimulated RAW264.7 cells with IC50 values of 8.01, 20.21, and 4.05 µM, respectively.