p-Quinone Methide-Mediated Nonenzymatic Formation of Chalcane-Containing Dimers in Dragon's Blood.

Chalcane-containing dimers are major compounds identified from dragon's blood, the red resin that accumulates in Dracaena trees after injury. The key step for the formation of these dimers was a p-quinone methide (p-QM, 3) mediated nonenzymatic Michael addition. Compound 3 is derived from the spontaneous dehydration of chalcane alcohol-M274 (2). Two dihydroflavonol-4-reductases, discovered in D. cambodiana, reduce dihydrochalcone-M272 (7) to 2. Moreover, the application potential of p-QMs was demonstrated using a 3-like p-QM to synthesize diverse dimeric derivatives.

New antifungal cycloheximide epimers produced by Streptomyces sp. YG7.

A couple of new cycloheximide epimers, 13(α)-acetoxy-anhydroisoheximide (1) and 13(ß)-acetoxy-anhydroisoheximide (2), together with six known compounds (3-8), were obtained from the cultures of Streptomyces sp. YG7. The structures were elucidated based on a comprehensive spectroscopic data analysis including 1D and 2D NMR, as well as HRESIMS, and by comparison with the literature. The X-ray crystal analysis of 1 further confirmed the structure. All the compounds were tested for antifungal activity. Compounds 1, 2 and 5-8 showed moderate Canidia albicans inhibitory activity, while 5 and 6 presented moderate Pyricularia oryzae inhibitory activity. [Formula: see text].

2-(2-Phenylethyl)chromone derivatives: Promising α-glucosidase inhibitors in agarwood from Aquilaria filaria.

Twelve undescribed 2-(2-phenylethyl)chromone derivatives, including one pair of enantiomers, together with eleven known ones, were isolated from the EtOAc extract of agarwood originating from Aquilaria filaria. All structures were elucidated by spectroscopic (NMR, UV, IR, MS) methods and compared with reported data in literatures. Twenty-one compounds were assessed for α-glucosidase inhibitory activity, which showed inhibition of α-glucosidase with IC50 values ranging between 7.8 ± 0.3 to 137.7 ± 3.0 µM (Acarbose, 743.4 ± 3.3 µM; Genistein, 8.3 ± 0.1 µM). Our results expanded the structural diversity of 2-(2-phenylethyl)chromones from agarwood, and revealed the potential of 2-(2-phenylethyl)chromones as α-glucosidase inhibitors.

[A new cytotoxic isoflavane from Dalbergiae Odoriferae Lignum].

Fourteen compounds were isolated from the ethanol extract of Dalbergiae Odoriferae Lignum by various chromatographic techniques, including column chromatographies on silica gel, Sephadex LH-20 and semi-preparative HPLC. Their structures were determined by spectroscopic techniques as S-3'-hydroxy-7,2',4'-trimethoxyisoxane(1), 2-(2',4'-dimethoxyphenyl)-6-hydroxybenzofuran(2), 2-(2'-hydroxy-4'-methoxyphenyl)-6-methoxybenzofuran(3), 7,2',4'-trimethoxydihydroisoflavone(4), sativanone(5), 3,9-dimethoxy-6H-benzofuro[3,2-c]chromen-6-one(6),(6 aS,11 aS)-homopterocarpin(7),(6 aS,11 aS)-8-hydroxy-3,9-dimethoxypterocarpan(8),(6 aS,11 aS)-3,8,9-trimethoxypterocarpan(9), isodalbergin(10), isoliquiritigenin(11), butein(12), butin(13) and 3,7,4'-trihydroxyflavone(14). Among them, compound 1 was a new compound, while 2 and 3 were new natural products, 6, 8, 9 and 14 were isolated for the first time from Dalbergiae Odoriferae Lignum. Compounds 1-14 were tested for their cytotoxic activity against human hepatoma cell line BEL-7402, human gastric cancer cell line SCG-7901, human lung cancer cell line A549, human chronic myeloid leukemia cell line K562 and HeLa human cervical cancer cellline by MTT method. Compound 1 exhibited significant cytotoxicity with IC_(50) values ranging from 2.85 to 11.62 µg·mL~(-1). In addition, 2, 11 and 12 showed weak cytotoxic activities.

Genetic diversity and genetic structure of Decalobanthus boisianus in Hainan Island, China.

Decalobanthus boisianus is a native plant of Hainan Island, China, which has caused considerable damage to tropical forest ecosystems in recent decades. Understanding the genetic diversity and structure of this species can facilitate uncovering the molecular mechanism of its invasive ability. Here, we collected 77 individuals of D. boisianus spanning 8 distribution areas with a gradient of human disturbance intensity (i.e., low, moderate, and high disturbance intensity groups) to assess patterns of genetic diversity and structure using inter simple sequence repeat (ISSR) markers. We found that a total of 220 loci were scored with 13 primers using ISSR methods, and that 198 loci were polymorphic. The genetic diversity of D. boisianus among these eight forests decreased with increasing human disturbance intensity. Over 70% of the total genetic variation was present within populations, while less than 30% of variation was found among populations. There was a high gene flow (1.27) among them due to a lack of effective geographic barriers. The mean Nei's genetic distance of D. boisianus populations was found to be relatively small (i.e., 0.07), and the average genetic similarity of the eight populations was high (i.e., 0.93). Our findings indicate that the genetic diversity of D. boisianus correlated to human disturbance density, and that D. boisianus populations in Hainan Island have frequent gene exchange. We suggest that reduce deforestation to decrease human disturbance may be a good way to prevent the invasion of D. boisianus.

Polyacetylenes from the Roots of Swietenia macrophylla King.

A phytochemical investigation of the roots of Swietenia macrophylla led to the isolation of seven polyacetylenes, including five new compounds (1-5) and two known ones (6-7). Their structures were elucidated by extensive spectroscopic analysis and detailed comparison with reported data. All the isolates were tested for their cytotoxicity against the human hepatocellular carcinoma cell line BEL-7402, human myeloid leukemia cell line K562, and human gastric carcinoma cell line SGC-7901. Compounds 1 and 6 showed moderate cytotoxicity against the above three human cancer cell lines with IC50 values ranging from 14.3 to 45.4 µM. Compound 4 displayed cytotoxicity against the K562 and SGC-7901 cancer cell lines with IC50 values of 26.2 ± 0.4 and 21.9 ± 0.3 µM, respectively.

Four new guaiane sesquiterpenoids from agarwood of Aquilaria filaria.

Six 8,12-epoxyguaiane sesquiterpenes (1-6), together with two known 2-(2-phenylethyl)chromone derivatives (7-8) were isolated from agarwood originating from Aquilaria filaria. Their structures were established by spectroscopic methods including IR, HRESIMS, 1D, and 2D NMR, and comparison with the published data. The absolute configuration of compound 1 was unambiguously determined by quantum chemical calculation of the electronic circular dichroism (ECD) spectrum. All compounds were tested for their α-glucosidase inhibitory activity and cytotoxicity. Compound 5 showed significant α-glucosidase inhibitory activity with IC50 value of 253.2 ±â€¯9.7 µM (Acarbose, 743. 4 ±â€¯3.3 µM). Compounds 2-4 displayed weak cytotoxicity against K562 tumor cell lines.

Two new compounds from the roots of Swietenia macrophylla.

Phytochemical investigation on the roots of Swietenia macrophylla yielded one new pharagmalin-type limonoid named 2-dehydroxyl-swietephragmin C (1) and one new xanthone, 1,5-dihydroxy-6-methoxy-6',6'-dimethyl-2H-pyrano[2',3':3,2]xanthone (2), in addition to three known compounds. The structures of the new compounds were unambiguously determined by comprehensive spectroscopic methods (NMR, UV, IR, MS), as well as by comparison with the reported data in the literature. Xanthones were reported from Swietenia genus for the first time.