Background: New semi-synthetic aminoglycoside antibiotics generally use chemical modifications to avoid inactivity from pathogens. One of the most used modifications is 3′,4′-di-deoxygenation, which imitates the structure of gentamicin. However, the mechanism of di-deoxygenation has not been clearly elucidated. Results: Here, we report that the bifunctional enzyme, GenB4, catalyzes the last step of gentamicin 3′,4′-di-deoxygenation via reduction and transamination activities. Following disruption of genB4 in wild-type M. echinospora, its products accumulated in 6′-deamino-6′-oxoverdamicin (1), verdamicin C2a (2), and its epimer, verdamicin C2 (3). Following disruption of genB4 in M. echinospora ΔgenK, its products accumulated in sisomicin (4) and 6′-N-methylsisomicin (5, G-52). Following in vitro catalytic reactions, GenB4 transformed sisomicin (4) to gentamicin C1a (9) and transformed verdamicin C2a (2) and its epimer, verdamicin C2 (3), to gentamicin C2a (11) and gentamicin C2 (12), respectively. Conclusion: This finding indicated that in addition to its transamination activity, GenB4 exhibits specific 4′,5′ double-bond reducing activity and is responsible for the last step of gentamicin 3′,4′-di-deoxygenation. Taken together, we propose three new intermediates that may refine and supplement the specific biosynthetic pathway of gentamicin C components and lay the foundation for the complete elucidation of di-deoxygenation mechanisms.

Alzheimer’s disease (AD) is a neurodegenerative disorder that affects millions of people worldwide. Acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) are promising therapeutic targets f...

Six sesquiterpenoids and four lignans (1–10) were isolated from the n-BuOH extract of the rhizomes of Atractylodes lancea. Among them, the new sesquiterpenoid glycoside named (4 R, 5S, 7R)-hinesolone-11-O-β-ᴅ-glucopyranoside (1), along with three known compounds (2–4) were first obtained from this genus. All the isolates were elucidated by spectroscopic analyses and chemical methods, and the absolute configurations were assigned by electronic circular dichroism spectroscopy technique. In addition, the cytotoxic bioassay of compound 1 was evaluated and results showed it had no significant antitumor activity against human cancer cell lines MCF-7, HepG-2 and Hela.

A large number of extracts of medicinal plants or natural products shows beneficial to combat obesity. In the present work, a new flavonoid named (2S,1″R,2″R)-4′-hydroxy-7-methoxy-6-(1,2,3-trihydroxy-3-methyl-butyl)-flavanone (1), along with seven known compounds (2–8) were isolated from the seeds of Cullen corylifolium. Their structures, including the absolute configurations, were determined by the analysis of comprehensive spectroscopic data and computational calculation methods. All isolates were evaluated for their diacylglycerol acyltransferase (DGAT) inhibitory activity. Compounds 1–4 exhibited different level of DGAT1 inhibitory activity with IC₅₀ values ranging from 28.2 ± 1.1 to 127.3 ± 1.9 μM. In addition, 45 flavonoids which be evaluated for DGAT inhibitory activity were summarised and potential structure–activity relationships were discussed. Graphical Abstract

Medicinal plants in the high salinity and high alkaline environment might possess some special chemical constituents with new skeleton and high bioactivity. In this work, the main chemical constituents of Limonium sinense, namely flavonoids, were comprehensively studied for the first time. A new flavonoid together with five known compounds were isolated from the whole plants of L. sinense. Their structures were determined by the analysis of comprehensive spectroscopic data. All isolates were evaluated for their anti-inflammatory activity. Compound 1 exhibited moderate anti-inflammatory activity on NO production with IC₅₀ value of 20.5 ± 1.3 μM. In addition, 38 flavonoids were identified by UPLC-MS/MS method and 18 reported flavonoids were summarised.

Saline-tolerant medicinal plants possess novel chemical constituents with high bioactivity because of their unique secondary metabolic pathways. Limonium sinense, an aquatic plant found in the coastal wetlands of the Yellow River Delta, was collected and studied in the present work. Ten drimane-type sesquiterpenoids and four triterpenoids, including six new ones (sinenseines A–F), were isolated from a whole plant of L. sinense for the first time. Their structures, including the absolute configurations, were determined by analyzing the comprehensive spectroscopic data. In addition, twelve terpenoids, including nine sesquiterpenoids, were identified using UPLC-MS/MS and GNPS methods. All isolates were evaluated for their antiproliferative and anti-inflammatory activities. Compounds 2–4, 6, 13, and 14 showed moderate anti-tumor effects on A549, H1299, HepG2 and A2780 cells with IC₅₀ values ranging from 35.2 ± 2.0 to 90.5 ± 3.1 μM. Furthermore, compound 1 exhibited significant anti-inflammatory activity with an IC₅₀ value of 8.3 ± 1.2 μM against NO production in LPS-induced RAW 264.7 macrophages.