A New 19(10→9)Abeo-Euphane Triterpenoid with other Terpenoid Components from Trichilia dregeana Leaves and their NO Production Inhibitory Activities in LPS-Stimulated RAW264.7 Macrophages.

Trichilia dregeana Sond. (Meliaceae) is a plant used in traditional medicine to treat wounds. The anti-inflammatory potential of the ethyl acetate leaf extract and the presence of euphane-type triterpenes in this extract have recently been reported by our group. Further investigation of the remaining subfractions of the ethyl acetate fraction afforded a new 19(10→9)abeo-euphane-type triterpenoid (1), along with six known terpenoids (2-7). The structure of the new compound was elucidated by analyses of the HR-ESI-MS, 1D and 2D NMR data and by comparison with previously reported data. We investigated the ability of the compounds to modulate the production of nitric oxide (NO) in LPS-stimulated RAW264.7 macrophages. The known compounds 3 and 6 exhibited moderate (IC50 72.06 µM) and mild (IC50 98.84 µM) inhibitory activities, respectively, without cytotoxic effects on the cells. These results, in conjunction with our previous findings, emphasize the significant role of terpenoid components in the anti-inflammatory efficacy of T. dregeana leaves and indicate that the rare 3,10-epoxy-19(10→9)abeo-euphane triterpenoids could serve as a chemotaxonomic marker for T. dregeana.

Five pimarane diterpenoids from Kaempferia champasakensis and their cytotoxic activities.

A phytochemical investigation of Kaempferia champasakensis rhizomes led to the isolation of five new pimarane diterpenes, kaempferiols E-I (1-5). The structures of 1-5 were elucidated by extensive spectroscopic techniques, including HR-ESI-MS, UV, IR, and 1D and 2D NMR. The absolute configurations of 1-3 were determined by the modified Mosher method, and those of 4 and 5 were established by ECD calculations. Further cytotoxic assay for all isolated compounds against three human cancer cell lines, lung cancer (A549), cervical cancer (HeLa), and breast cancer (MCF-7) indicated that 5 showed moderate cytotoxic activities against the three tested cell lines, with IC50 values of 44.78, 25.97, and 41.39 Mµ for A549, HeLa, and MCF-7 cell lines, respectively.

Three neo-Clerodane Diterpenoids from Tinospora cordifolia Stems and Their Arginase Inhibitory Activities.

Three neo-clerodane diterpenoids, including two new tinocordifoliols A (1) and B (2) and one known tinopanoid R (3), were isolated from the ethyl acetate-soluble fraction of the 70% ethanol extract of Tinospora cordifolia stems. The structures were elucidated by various spectroscopic methods, including one dimensional (1D) and 2D-NMR, high resolution-electrospray ionization (HR-ESI)-MS, and electronic circular dichroism (ECD) data. The T. cordifolia extract and all isolated compounds 1-3 possessed arginase I inhibitory activities. Among them, 3 exhibited moderate competitive inhibition of human arginase I (IC50 = 61.9 µM). Furthermore, docking studies revealed that the presence of a ß-substituted furan in 3 may play a key role in the arginase I inhibitory activities.

New 19(10 → 9)abeo-euphane-type triterpenoids from Trichilia dregeana leaves and NO production inhibitory activities.

Phytochemical investigation of the EtOAc soluble fraction from leaves of Trichilia dregeana Sond. (Meliaceae) afforded naturally rare four new pentacyclic triterpenoids (1-4), together with five known pentacyclic analogs (5-8, and 11) and two steroids (9 and 10). Their structures were elucidated by extensive spectroscopic techniques such as 1D and 2D NMR and HRESIMS data analyses. The absolute configuration of 1 was determined by using the single-crystal X-ray diffraction analysis. The nitric oxide (NO) production inhibitory assay indicated that the EtOAc fraction as well as 4 and 7 inhibited the NO production in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells with the IC50 values of 83.53 µg/mL and 81.31 and 85.71 µM, respectively. Compounds 1-4 are rare 19(10 â†’ 9)abeo-euphane-type triterpenoids bearing a 3,10-ether bridge. To the best of our knowledge, this study is the first isolation of triterpenoids with the 3,10-ether bridge in their skeleton from the genus Trichilia, providing new insights into the chemodiversity of the terpenoids in T. dregeana.

A new 3,4-seco-isopimarane and three new isopimarane diterpenoids from Kaempferia champasakensis collected from Vietnam and their cytotoxic activities.

A phytochemical investigation of Kaempferia champasakensis rhizomes led to the isolation of a new 3,4-seco-isopimarane diterpene, kaempferiol A (1), and three new isopimarane diterpenes, kaempferiols B-D (2-4), together with six known isopimarane diterpenes (5-10). The structures of 1-4 were elucidated by extensive spectroscopic analyses, including HR-ESI-MS, UV, IR, and 1D and 2D NMR. The absolute configurations of 1, 3, and 4 were determined by ECD calculations, while that of 2 was established using the modified Mosher method. All isolated compounds were tested for cytotoxicity against three human cancer cell lines, lung cancer (A549), cervical cancer (HeLa), and breast cancer (MCF-7). Among them, 6 and 7 showed moderate cytotoxic activities against the three tested cell lines, with IC50 values ranging from 38.04 to 27.77 µM, respectively.

Substrate-Dependent Alteration in the C- and O-Prenylation Specificities of Cannabis Prenyltransferase.

CsPT4 is an aromatic prenyltransferase that synthesizes cannabigerolic acid (CBGA), the key intermediate of cannabinoid biosynthesis in Cannabis sativa, from olivetolic acid (OA) and geranyl diphosphate (GPP). CsPT4 has a catalytic potential to produce a variety of CBGA analogs via regioselective C-prenylation of aromatic substrates having resorcylic acid skeletons including bibenzyl 2,4-dihydroxy-6-phenylethylbenzoic acid (DPA). In this study, we further investigated the substrate specificity of CsPT4 using phlorocaprophenone (PCP) and 2',4',6'-trihydroxydihydrochalcone (THDC), the isomers of OA and DPA, respectively, and demonstrated that CsPT4 catalyzed both C-prenylation and O-prenylation reactions on PCP and THDC that share acylphloroglucinol substructures. Interestingly, the kinetic parameters of CsPT4 for these substrates differed depending on whether they underwent C-prenylation or O-prenylation, suggesting that this enzyme utilized different substrate-binding modes suitable for the respective reactions. Aromatic prenyltransferases that catalyze O-prenylation are rare in the plant kingdom, and CsPT4 was notable for altering the reaction specificity between C- and O-prenylations depending on the skeletons of aromatic substrates. We also demonstrated that enzymatically synthesized geranylated acylphloroglucinols had potent antiausterity activity against PANC-1 human pancreatic cancer cells, with 4'-O-geranyl THDC being the most effective. We suggest that CsPT4 is a valuable catalyst to generate biologically active C- and O-prenylated molecules that could be anticancer lead compounds.

Catalytic Potential of Cannabis Prenyltransferase to Expand Cannabinoid Scaffold Diversity.

Biologically active cannabinoids are derived from cannabigerolic acid (CBGA), which is biosynthesized by aromatic prenyltransferase CsPT4. We exploit the catalytic versatility of CsPT4 to synthesize various CBGA analogues, including a geranylated bibenzyl acid, the precursor to bibenzyl cannabinoids of liverwort origin. The synthesized natural and new-to-nature cannabinoids exhibit potent cytotoxicity in human pancreatic cancer cells. CsPT4 can artificially extend the cannabinoid biosynthetic diversity with novel and improved biological activities.

Phenolic Derivatives with Anti-Acetylcholinesterase Inhibitory Activities from Galeola nudifolia in Vietnam.

A new phenolic derivative, galeomalate A (1), together with five known structurally related compounds (2-6), was isolated from the ethyl acetate extract of Galeola nudifolia collected in Vietnam. The structures were elucidated by various spectroscopic methods, including 1D and 2D NMR, HR-ESI-TOF-MS, and CD data, and chemical conversion of the sugar moiety. All isolated compounds possessed acetylcholinesterase (AChE) inhibitory activities in a dose-dependent manner. Among them, compounds 2 and 3 exhibited the first and second highest inhibitory activity on AChE with IC50 values of 122.13 and 125.49 µM, respectively. Compounds 1 and 4-6 inhibited the AChE activity by mixed modes of action comprising competitive and non-competitive modes, whereas 2 and 3 exerted their inhibitory activities in a competitive manner. Molecular docking analyses suggested that the phenyl-ß-D-glucopyranoside unit of 2 and 3 bound to the active site of AChE for the competitive inhibitory activities, while the mixed inhibitory activity of 4 was due to the two binding patterns in the active-site and the active-site entrance of AChE. Furthermore, the docking studies indicated that 1, 5, and 6 would inhibit AChE in a mixed inhibitory manner by adopting three distinct binding patterns of the additional phenyl-ß-D-glucopyranoside unit at the active-site entrance.

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.

Novel insights into the antibacterial activities of cannabinoid biosynthetic intermediate, olivetolic acid, and its alkyl-chain derivatives.

Investigations of antibacterial activities revealed that the incorporation of longer alkyl chains to the C-6 position in resorcylic acid conferred antibacterial properties against Staphylococcus aureus and Bacillus subtilis. The resultant olivetolic acid (OA) derivatives with n-undecyl and n-tridecyl side-chains, even those lacking the hydrophobic geranyl moiety from their C-3 positions, exhibited strong antibacterial activities against B. subtilis at a MIC value of 2.5 µM. Furthermore, the study demonstrated that the n-heptyl alkyl-chain modification at C-6 of cannabigerolic acid (CBGA) effectively enhanced the activity against B. subtilis, demonstrating the importance of the alkyl side-chain in modulating the bioactivity. Overall, the findings in this study provided insight into further evaluations of the antibacterial activities, as well as other various biological activities of OA and CBGA derivatives, especially with optimized hydrophobicities at both the alkyl and prenyl side-chain positions of the core skeleton for the discovery of novel drug seeds.

Seco- and isopimarane diterpenoids from Kaempferia marginata rhizomes and their NO inhibition activities.

Three undescribed 9,10-seco-isopimarane diterpenoids, marginols I-K, and an unprecedent isopimara-8(9),15-diene diterpene, 14-epi-boesenberol F, together with a known 9,10-seco-isopimarane diterpenoid, kaemgalangol A, were isolated from the rhizomes of Vietnamese Kaempferia marginata. Marginols I and J contained a naturally very rare 6-oxabicyclo[3.2.1]octane-5-ol ring, while marginol K had a naturally rare oxepan-2-one ring in its structure. The unprecedented structures were elucidated by spectroscopic techniques, including HR-ESI-TOF-MS, UV, IR, and 1D and 2D NMR. The absolute configurations of marginols I-K and 14-epi-boesenberol F were determined by ECD calculations. The NO production inhibitory assay revealed that the isolated compounds, except marginol J, exhibited NO inhibitory activities with IC50 values ranging from 65.06 to 87.70 µM against lipopolysaccharide (LPS)-induced RAW264.7 cells.

Bioinspired computational design of lankacidin derivatives for improvement in antitumor activity.

Background: The 17-membered polyketide, lankacidin C, exhibits considerable antitumor activity as a microtubule stabilizer by binding to the paclitaxel binding site. Method: Esterification of the C-7/C-13 hydroxyl in lankacidin C was performed with acetyl, cinnamoyl and hydrocinnamoyl groups and their antitumor activity was assessed to improve the cytotoxicity of lankacidins through bioinspired computational design. Results: Compared with the cytotoxicity of parent lankacidin C against the HeLa cell line, 13-O-cinnamoyl-lankacidin C demonstrated sevenfold higher cytotoxicity. Furthermore, 7,13-di-O-cinnamoyl-lankacidin C exhibited considerable antitumor activity against three tested cell lines. Conclusion: C13-esterification by a cinnamoyl group dramatically improved antitumor activity, in agreement with computational predictions. This finding provides a potential substrate for next-generation lankacidin derivatives with significant antitumor activity.

Cytotoxic potential of dihydrochalcones from Eriosema glomeratum and their semi-synthetic derivatives.

In the search of cytotoxic dihydrochalcones, this investigation led to the isolation of seven compounds (1-7) from Eriosema glomeratum and the preparation of eight derivatives (8-15). The cytotoxicity of samples was evaluated against lung (A549), breast (MCF-7), and cervical (HeLa) human cancer cells. The CH2Cl2/MeOH extract of the aerial part had strong cytotoxicity against all cells [IC50 11.2 (MCF-7), 8.4 (HeLa) and 13.1 (A549) µg/mL]. A strong activity was also displayed by the n-hexane fraction on MCF-7 (IC50 11.2 µg/mL). The precursor 3 and the derivative 8 were specifically found as strong cytotoxic agents toward MCF-7 (7.6 µM) and HeLa (3.1 µM), respectively and were more effective than the positive control. Derivatives 8 (3.1 µM) and 9 (21.3 µM) against HeLa were most potent than their precursor 3 (23.7 µM). This is the first preparation of 8-14 as well as the cytotoxicity of 3, 4, 8-15, fractions, and extract.

Catalytic potential of a fungal indole prenyltransferase toward ß-carbolines, harmine and harman, and their prenylation effects on antibacterial activity.

The prenylation of compounds has attracted much attention, since it often adds bioactivity to non-prenylated compounds. We employed an enzyme assay with CdpNPT, an indole prenyltransferase from Aspergillus fumigatus with two naturally occurring ß-carbolines, harmine (3) and harman (4) as prenyl acceptors, in the presence of dimethylallyl diphosphate (DMAPP) as the prenyl donor. The enzyme accepted these two prenyl acceptor substrates to produce 6-(3',3'-dimethylallyl)harmine (5) from 3 and 9-(3',3'-dimethylallyl)harman (6) and 6-(3',3'-dimethylallyl)harman (7) from 4. The X-ray crystal structure analysis of the CdpNPT (38-440) truncated mutant complexed with 4, and docking simulation studies of DMAPP to the crystal structure of the CdpNPT (38-440) mutant, suggested that CdpNPT could employ the two-step prenylation mechanism to produce 7, while the enzyme produced 6 with either one- or two-step prenylation mechanisms. Furthermore, the antibacterial assays revealed that the 3',3'-dimethylallylation of 3 and 4, as well as harmol (1), at C-6 enhanced the activities against Staphylococcus aureus and Bacillus subtilis.

Enzymatic formation of a prenyl ß-carboline by a fungal indole prenyltransferase.

CdpNPT from Aspergillus fumigatus is a fungal indole prenyltransferase (IPT) with remarkable substrate promiscuity to generate prenylated compounds. Our first investigation of the catalytic potential of CdpNPT against a ß-carboline, harmol (1), revealed that the enzyme also accepts 1 as the prenyl acceptor with dimethylallyl diphosphate (DMAPP) as the prenyl donor and selectively prenylates the C-6 position of 1 by the "regular-type" dimethylallylation to produce 6-(3-dimethylallyl)harmol (2). Furthermore, our X-ray crystal structure analysis of the C-His6-tagged CdpNPT (38-440) truncated mutant complexed with 1 and docking studies of DMAPP to the crystal structure of the CdpNPT (38-440) mutant suggested that CdpNPT could employ the two-step prenylation system to produce 2.

Identification of a diarylpentanoid-producing polyketide synthase revealing an unusual biosynthetic pathway of 2-(2-phenylethyl)chromones in agarwood.

2-(2-Phenylethyl)chromones (PECs) are the principal constituents contributing to the distinctive fragrance of agarwood. How PECs are biosynthesized is currently unknown. In this work, we describe a diarylpentanoid-producing polyketide synthase (PECPS) identified from Aquilaria sinensis. Through biotransformation experiments using fluorine-labeled substrate, transient expression of PECPS in Nicotiana benthamiana, and knockdown of PECPS expression in A. sinensis calli, we demonstrate that the C6-C5-C6 scaffold of diarylpentanoid is the common precursor of PECs, and PECPS plays a crucial role in PECs biosynthesis. Crystal structure (1.98 Å) analyses and site-directed mutagenesis reveal that, due to its small active site cavity (247 Å3), PECPS employs a one-pot formation mechanism including a "diketide-CoA intermediate-released" step for the formation of the C6-C5-C6 scaffold. The identification of PECPS, the pivotal enzyme of PECs biosynthesis, provides insight into not only the feasibility of overproduction of pharmaceutically important PECs using metabolic engineering approaches, but also further exploration of how agarwood is formed.

Marginols A‒H, unprecedented pimarane diterpenoids from Kaempferia marginata and their NO inhibitory activities.

Kaempferia marginata rhizomes are used as an herb in food and as traditional medicine for the treatment of inflammatory-related diseases in Asian countries. In contrast to the previously reported phytochemical investigation of Thai and Chinese K. marginata rhizomes, which demonstrated the presence of sandaracopimaradiene and ent-sandaracopimaradiene, our first investigation of Vietnamese K. marginata rhizomes led to the isolation of eight undescribed pimarane diterpenoids, marginols A‒H, along with 18 known pimarane diterpenoids. The structures of these compounds were elucidated by spectroscopic techniques, including 1D and 2D NMR, HRESIMS, and CD spectroscopy and/or by comparisons of their NMR data with previously reported data. Furthermore, evaluations of the NO production inhibitory activity against LPS-stimulated RAW264.7 cells revealed that the undescribed compounds, marginols B and D‒G, and the known compounds, sandaracopimaradien-6ß,9α-diol-1-one and 6-acetoxysandaracopimardien-9-ol-1-one, showed potent activities. These results provide insights into the chemodiversity of Vietnamese K. marginata rhizomes as well as their traditional usage from the viewpoint of their chemical constituents.

Dual Engineering of Olivetolic Acid Cyclase and Tetraketide Synthase to Generate Longer Alkyl-Chain Olivetolic Acid Analogs.

The therapeutic effects of Δ9-tetrahydrocannabinol (Δ9-THC) can be enhanced by modifications of the pentyl moiety at C-3. The engineering of Cannabis sativa olivetolic acid cyclase and tetraketide synthase with F24I and L190G substitutions, respectively, in the biosynthesis of Δ9-THC serves as a platform for the generation of resorcylic acids up to 6-undecylresorcylic acid. These results provide insights into the development of THC analogs with chemically distinct acyl moieties at C-3.

Chemoenzymatic synthesis, computational investigation, and antitumor activity of monocyclic lankacidin derivatives.

We investigated the importance of the δ-lactone ring (C1-C5) in lankacidin C using chemoenzymatic synthesis and computational prediction and assessing biological activity, including antitumor activity. Pyrroloquinoline quinone-dependent dehydrogenase (Orf23) in Streptomyces rochei was used in the chemoenzymatic synthesis of lankacyclinone C, a novel lankacidin C congener lacking the δ-lactone moiety. Orf23 could convert the monocyclic lankacidinol derivatives, lankacyclinol and 2-epi-lankacyclinol, to the C-24 keto compounds, lankacyclinone C and 2-epi-lankacyclinone C, respectively, elucidating the relaxed substrate specificity of Orf23. Computational prediction using molecular dynamics simulations and the molecular mechanics/generalized Born-surface area protocol indicated that binding energy values of all the monocyclic derivatives are very close to those of lankacidin C, which may reflect a comparable affinity to tubulin. Monocyclic lankacidin derivatives showed moderate antitumor activity when compared with bicyclic lankacidins, suggesting that the δ-lactone moiety is less important for antitumor activity in lankacidin-group antibiotics.

Flavanols and Flavanes from Crinum asiaticum and Their Effects on LPS Signaling Pathway Through the Inhibition of NF-κB Activation.

Three new flavanols, (2R,3S)-7-methoxy-flavan-3-ol (1: ), (2R,3S)-7-hydroxy-flavan-3-ol (2: ), and (2R,3S)-2'-hydroxy-7-methoxy-flavan-3-ol (3: ), together with two known flavans (4: and 5: ), were isolated from the chloroform extract of Crinum asiaticum. Their structures were elucidated by various spectroscopic methods, including 1D and 2D NMR, HR-ESI-MS, and CD data. The isolated compounds 1: and 3: -5: showed inhibitory activity toward LPS-induced nitric oxide (NO) production. Further investigation of the NF-κB pathway mechanisms indicated that 1: and 3: -5: inhibited the LPS-induced IL-6 production and p65 subunit phosphorylation of NF-κB in RAW264.7 cells, with an effective dose of 10 µM.