Substrate Flexibilities of Norbelladine Synthase and Noroxomaritidine/Norcraugsodine Reductase for Hydroxylated and/or Methoxylated Aldehydes.

Amaryllidaceae alkaloids are structurally diverse natural products with a wide range biological properties, and based on the partial identification of the biosynthetic enzymes, norbelladine would be a common intermediate in the biosynthetic pathways. Previous studies suggested that norbelladine synthase (NBS) catalyzed the condensation reaction of 3,4-dihydroxybenzaldehyde and tyramine to form norcraugsodine, and subsequently, noroxomaritidine/norcraugsodine reductase (NR) catalyzed the nicotinamide adenine dinucleotide phosphate (NADPH)-dependent reduction of norcraugsodine to generate norbelladine. However, recent studies have highlighted possible alternative Amaryllidaceae alkaloid biosynthetic pathways via the formation of isovanillin and vanillin from the 4-O- and 3-O-methylation reactions of 3,4-dihydroxybenzaldehyde, respectively. Herein, we focused on NpsNBS and NpsNR, which were initially identified from Narcissus pseudonarcissus, and explored their substrate recognition tolerance by performing condensation reactions of tyramine with various benzaldehyde derivatives, to shed light on the Amaryllidaceae alkaloid biosynthetic pathway from the viewpoint of the enzymatic properties. The assays revealed that both NpsNBS and NpsNR lacked the abilities to produce 4'-O- and 3'-O-methylnorbelladine from isovanillin and vanillin with tyramine, respectively. These observations thus suggested that Amaryllidaceae alkaloids are biosynthesized from norbelladine, formed through the condensation/reduction reaction of 3,4-dihydroxybenzaldehyde with tyramine.

Dryoptkirbioside, A New Fructofuranoside Glycerol, and Other Constituents from Dryopteris kirbi Hook et Grav Rhizomes.

A new fructofuranoside glycerol, dryoptkirbioside (1), along with thirteen known compounds (2-14), was isolated from the MeOH extract of Dryopteris kirbi rhizomes by silica gel column chromatography, Sephadex LH-20 column chromatography, and semipreparative HPLC. The structure of the new compound was determined by analyses of its spectroscopic data including nuclear magnetic resonance (NMR), and high-resolution electrospray ionisation mass spectrometry (HR-ESI-MS) and chemical conversions. The hexane-soluble portion and the EAFA fraction showed strong activities against lung (A549), breast (MCF-7), and cervical (HeLa) human cancer cell lines (IC50 values ranging from 4.0 to 8.8 µg/mL). Aspidinol P (5) and aspidinol B (6) exhibited moderate to low cytotoxicity on the three cell lines (IC50 values ranging from 20.4 to 58.7 µM). The MeOH extract and hexane-soluble portion had excellent activities against Staphylococcus aureus and Bacillus subtilis (MICs 11.7 and 23.4 µg/mL), whereas the AcOEt- and BuOH-soluble portions were significantly active on S. aureus (MICs 46.9 and 93.8 µg/mL). The main fractions EAFB , EAFC and nBFB displayed excellent activity against S. aureus (MICs 11.7 and 23.4 µg/mL). Aspidinol B (6) had significant activity, while aspidinol P (5) was moderately active against S. aureus and B. subtilis (MICs 42.0 and 89.5 µM).

Arginase inhibitory activities of guaiane sesquiterpenoids from Curcuma comosa rhizomes.

Arginases are bimanganese enzymes involved in many human illnesses, and thus are targets for disease treatments. The screening of traditional medicinal plants demonstrated that an ethanol extract of Curcuma comosa rhizomes showed significant human arginase I and II inhibitory activity, and further fractionation led to the isolation of three known guaiane sesquiterpenoids, alismoxide (1), 7α,10α-epoxyguaiane-4α,11-diol (2) and guaidiol (3). Tests of their inhibitory activities on human arginases I and II revealed that 1 exhibited selective and potent competitive inhibition for human arginase I (IC50 = 30.2 µM), whereas the other compounds lacked inhibitory activities against human arginases. To the best of our knowledge, this is the first demonstration of human arginase I inhibitory activity by a sesquiterpenoid. Thus, 1 is a primary and specific inhibitory molecule against human arginase I.

Shanpanootols G and H, Diterpenoids from the Rhizomes of Kaempferia pulchra Collected in Myanmar and Their Vpr Inhibitory Activities.

Two new trihydroxy derivative of Δ8(14),15-isopimarane diterpenoids, shanpanootols G (1) and H (2), along with three known analogues were isolated from the ethyl acetate-soluble extract of Kaempferia pulchra rhizomes collected in Shan State of Myanmar. The structures of these compounds including their absolute configurations were elucidated by the combination of one dimensional (1D) and 2D-NMR spectroscopic methods, high resolution mass spectrometric technique, and the experimental and the calculated electronic circular dichroism (ECD) data. The isopimarane diterpenoids (1-5) were tested for their Viral protein R (Vpr) inhibitory activities against TREx-HeLa-Vpr cells. Shanpanootol H (2) and (1R,2S,5S,9R,10S,13R)-1,2-dihydroxypimara-8(14),15-dien-7-one (4) exhibited anti-Vpr activities at the 5 µM treated dose.

Shanpanootols A-F, diterpenoids from Kaempferia pulchra rhizomes collected in Myanmar and their Vpr inhibitory activities.

Six new isopimarane diterpenoids, shanpanootols A-F (1-6), along with two known analogues, were isolated from the ethyl acetate-soluble extract of Kaempferia pulchra rhizomes collected in Myanmar. The structures of these compounds were elucidated by extensive spectroscopic techniques such as 1D and 2D NMR and HRESIMS. The absolute configuration of 1 was determined by the modified Mosher method. The new isolates (1-6) were tested for their Vpr inhibitory activities against TREx-HeLa-Vpr cells. Shanpanootols C (3) and E (5) inhibited Vpr at doses of 2.5 and 5 µM, respectively.

Deciphering the Biosynthetic Mechanism of Pelletierine in Lycopodium Alkaloid Biosynthesis.

Pelletierine, a proposed building block of Lycopodium alkaloids (LAs), was demonstrated to be synthesized via the non-enzymatic Mannich-like condensation of Δ1-piperideine and 3-oxoglutaric acid produced by two new type III PKSs (HsPKS4 and PcPKS1) characterized from Huperzia serrata and Phlegmariurus cryptomerianus, respectively. The findings provide new insights for further understanding the biosynthesis of LAs such as huperzine A.