Ying-Ying Chen

Melokhanines A–J, Bioactive Monoterpenoid Indole Alkaloids with Diverse Skeletons from Melodinus khasianus

The new melokhanines A-J (1-10) and 22 known (11-32) alkaloids were isolated from the twigs and leaves of Melodinus khasianus. The new compounds and their absolute configurations were elucidated by extensive analysis of spectroscopic, X-ray diffraction, and computational data. Melokhanine A (1), composed of a hydroxyindolinone linked to an octahydrofuro[2,3-b]pyridine moiety, is an unprecedented monoterpenoid indole alkaloid. Melokhanines B-H (2-8) possess a new 6/5/5/6/6 pentacyclic indole alkaloid skeleton. Alkaloids 1-16, 25-27, 31, and 32 showed the best antibacterial activity against Pseudomonas aeruginosa (MIC range 2-22 μM). Among the seven dermatophytes tested, compound 1 showed significant inhibitory activity against Microsporum canis, M. ferrugineum, and Trichophyton ajelloi (MIC range 38-150 μM), i.e., half the efficacy of the positive control, griseofulvin.

Antibacterial monoterpenoid indole alkaloids from Alstonia scholaris cultivated in temperate zone

Three new monoterpenoid indole alkaloids, named normavacurine-21-one (1), 5-hydroxy-19, 20-E-alschomine (2), and 5-hydroxy-19, 20-Z-alschomine (3), together with thirteen known indole alkaloids (4-16) were isolated from the leaves of Alstonia scholaris cultivated in Kunming. Their structures were elucidated on the basis of extensive spectroscopic analysis, as well as by comparison with the reported spectroscopic data. The leaves of A. scholaris cultivated in Kunming, contained picrinine-type alkaloids, scholaricin-type alkaloids and nareline as major alkaloids. New compounds 1-3 might be derived from a common biogenetic precursor (5). Compounds 1, 5 and 10 exhibited significant antibacterial activity against Enterococcus faecalis, and 3, 9 and 14 against Pseudomonas aeruginosa with an MIC value of 0.781 μg/mL, while 14 showed moderate activity against Klepsiella pneumonia with an MIC value of 1.56 μg/mL.

Monoterpenoid Indole Alkaloids from Inadequately Dried Leaves of Alstonia scholaris.

Six new indole alkaloids, named alstoniascholarines L–Q (1–6), together with nineteen known analogues were isolated from the inadequately dried leaves of Alstonia scholaris. Their structures were elucidated on the basis of extensive analysis of spectroscopic data and by comparison of their physical and spectroscopic data with the literature values. In addition, the new alkaloids were tested for their cytotoxic and neurite outgrowth-promoting activities.

New Cytotoxic Tigliane Diterpenoids from Croton caudatus.

Three new tigliane-type diterpenoids were isolated from the methanolic extract of the twigs and leaves of Croton caudatus, trivially named crotusins A-C (1-3). The structures of compounds 1-3 were elucidated on the basis of extensive spectral methods. These new compounds were highly oxygenated and heavily substituted. Cytotoxic activity against five human tumor cell lines was assessed for compounds 1-3 of which compound 3 showed significant inhibitory activity with IC50 values ranging from 0.49 to 4.19 µM against these cells, while crotusins A and B exhibited moderate activity.

Limonoid and Steroidal Saponin from Azadirachta indica

A new limonoid, 17-(5-methoxy-2-oxofuran-3-yl)-28-deoxonimbolide (1), and a new C21 steroidal saponin, 2α,4α-dihydroxy-pregn-5-en-16-one-3α-O-d-glucopyranoside (2), together with 11 known compounds were isolated from the methanol extract of the leaves of Azadirachta indica. The structures were elucidated by means of spectroscopic analysis and putative biosynthetic origins. All the compounds were evaluated for their antibacterial activities against six bacterial strains.Graphical Abstract

Polyphenolic compounds from Malus hupehensis and their free radical scavenging effects

Abstract One new 4-chromanone glycoside, 5-O-β-d-glucopyranoside-4-chromanone (1), together with 21 known polyphenols, was isolated from the leaves of Malus hupehensis. Their structures were elucidated on the basis of extensive spectroscopic methods including NMR (1D and 2D), mass (ESIMS and HRESIMS), IR, and by comparison with the data reported in the literature. Some of the isolated compounds were screened for antioxidant activity. Compounds 18 and 14 exhibited significant antioxidant activities with SC50 values 2.73 and 2.91 μg/mL, respectively, while 17, 19, 11, 7, 20, 22, 12 and 13 exhibited moderate activities with SC50 values ranging from 5.24–11.86 μg/mL. The HPLC fingerprint profiles of the leaves and fruits extracts were also analysed, which showed that the constituents were almost the same in both the extracts except for the content of phlorizin which was present in higher amount in the leaves.

Spiralosides A-C, Three New C27-Steroidal Glycoalkaloids from the Fruits of Solanum spirale.

Three new C27-steroidal glycoalkaloids, spiralosides A–C (1–3), were obtained from the total alkaloids of Solanum spirale by chromatographic methods. On the basis of spectroscopic evidence, spiralosides A–C were elucidated as (22R,25S)-22,26-epiminocholest-5-ene-3β,16α-diol-N-acetyl-3-O-α-l-rhamnopyranosyl-(1→4)-β-d-glucopyranosyl (1), (22R,25S)-22,26-epiminocholest-5-ene-3β,16α-diol-N-acetyl-3-O-β-d-glucopyranosyl (2), (22R,25S)-22,26-epiminocholest-3β,16α-diol-N-acetyl-3-O-β-d-glucopyranosyl (3), respectively. The total alkaloids of S. spirale have been screened for their antitussive and expectorant effects in intact animal model.Graphical Abstract