Phytochemical investigation of dichloromethane neutral phase of stem bark ofNauclea pobeguiniiled to the isolation of a new monoterpene indole alkaloid, pobeguinine1along with 14 known compounds including (−)-naucleofficine D (2a), (+)-naucleofficine D (2b), naucleidinal (3), quafrinoic acid (4), betulinic acid (5), ursolic acid (6), quinovic acid (7), quinovic acid 3-O-α-L-rhamnopyranoside (8a), quinovic acid 3-O-β-D-fucopyranoside (8b), β-sitosterol (9), β-sitosterol 3-O-β-D-glucopyranoside (10), benzoic acid (11), lacceroic acid (12) andn-heptacosane (13). The structure of compound1was unambiguously assigned on the basis of single-crystal X-ray diffraction technique. The Hirshfeld surface analysis was further carried out to quantitatively analyze the role of various types of hydrogen bonding in crystal stability. These structures were elucidated using spectroscopic methods. The isolates were evaluated for their radical scavenging properties as well as inhibitory activities against urease and tyrosinase enzymes with IC50values ranging from 13.4 to 58.9, 46.0 to 86.7 and 39.4 to 87.1 μg/mL, respectively. Compound6exhibited maximum radical scavenging activity with IC5013.4 μg/mL, while compound4exhibited maximum tyrosinase with IC5039.4 μg/mL. All the isolates showed moderate urease inhibition.
A new lignan, meiocarpin, and the known compounds, sitosterol and polycarpol, have been isolated from the stem bark of Meiocarpidium lepidotum, Annonaceae. The structure of the new compound was elucidated on the basis of its spectroscopic data.
Urease enzyme (UE) has been reported to be a potent virulence factor for Helicobacter pylori (HP) bacteria indicated to be responsible for various gastrointestinal diseases. Therefore, the spread of HP, currently regarded by the World Health Organization as a class 1 carcinogen, could be better controlled by targeting UE. It is in this line that we have synthesized three new derivatives (2–4) of the naturally occurring olean-12-en-3-one (1), which was previously isolated from the figs of Ficus vallis-choudae Delile (Moraceae). Among the synthesized compounds, 3 and 4 contain an indole moiety. Their structures were unambiguously assigned by spectroscopic and spectrometric techniques (1D-NMR, 2D-NMR and MS). The starting material and the synthesized compounds were screened for UE inhibition activity, and showed significant activities with IC50 values ranging from 14.5 to 24.6 μM, with compound (1) being the most potent as compared to the positive control thiourea (IC50 = 21.6 μM). Amongst the synthetic derivatives, compound 4 was the most potent (IC50 = 17.9 μM), while the others showed activities close to that of the control. In addition, molecular docking study of target compounds 2–4 was performed in an attempt to explore their binding mode for the design of more potent UE inhibitors.Graphical Abstract
Electronic supplementary materialThe online version of this article (10.1007/s13659-018-0193-7) contains supplementary material, which is available to authorized users.
Three previously undescribed indole alkaloids, named latifolianine A (1) and latifoliaindoles A and B (2 and 3), along with 10 known compounds (4−13), were isolated from the heartwood of Nauclea latifolia. Their structures were elucidated based on the analysis of their NMR and MS data. Latifolianine A (1) represents an unusual and unprecedented monoterpene indole alkaloid unit condensed with an ursanetype pentacyclic triterpenoid moiety. Plausible biogenetic routes toward latifolianine A (1) and latifoliaindoles A and B (2 and 3) were proposed. All the isolates were assessed in vitro for their inhibitory effects on Haemophilus influenzae. Naucleidinal (7) exhibited potent antibacterial activity (MIC value of 3.1 μg/mL) as compared to a reference drug, ciprofloxacin (MIC value of 1.6 μg/mL).
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