<Emphasis Type="Italic">S</Emphasis> genotyping and <Emphasis Type="Italic">S</Emphasis> screening utilizing <Emphasis Type="Italic">SFB</Emphasis> gene polymorphism in Japanese plum and sweet cherry by dot-blot analysis

Most Rosaceae fruit trees such as Japanese plum and sweet cherry have a gametophytic self-incompatibility (GSI) system controlled by a single S locus containing at least two linked genes with multiple alleles, i.e., S-RNase as a pistil determinant and SFB (S-haplotype-specific F-box gene) as a candidate for the pollen S determinant. For identification of S genotypes, many methods based on polymerase chain reaction (PCR) utilizing polymorphism in length of the S-RNase and SFB gene have been developed. In this study, we developed two dot-blot analysis methods for S-haplotype identification utilizing allele-specific oligonucleotides based on the SFB-HVa region, which has high sequence polymorphism. Dot-blotting of allele-specific oligonucleotides hybridized with digoxigenin-labeled PCR products allowed S genotyping of plants with nine S haplotypes (S-a, S-b, S-c, S-e, S-f, S-h, S-k, S-7 and S-10) in Japanese plum and ten S haplotypes (S-1, S-2, S-3, S-4, S-4′, S-5, S-6, S-7, S-9 and S-16) in sweet cherry (dot-blot-S-genotyping). In addition, dot-blotting of PCR products of SFB probed with the allele-specific oligonucleotides, occasionally utilizing competitive hybridization, was successful in screening for a desirable S haplotype in sweet cherry (dot-blot-S-screening).     

Identification of a canonical SCFSLF complex involved in S-RNase-based self-incompatibility of Pyrus (Rosaceae)

S-RNase-based self-incompatibility (SI) is an intraspecific reproductive barrier to prevent self-fertilization found in many species of the Solanaceae, Plantaginaceae and Rosaceae. In this system, S-RNase and SLF/SFB (S-locus F-box) genes have been shown to control the pistil and pollen SI specificity, respectively. Recent studies have shown that the SLF functions as a substrate receptor of a SCF (Skp1/Cullin1/F-box)-type E3 ubiquitin ligase complex to target S-RNases in Solanaceae and Plantaginaceae, but its role in Rosaceae remains largely undefined. Here we report the identification of two pollen-specific SLF-interacting Skp1-like (SSK) proteins, PbSSK1 and PbSSK2, in Pyrus bretschneideri from the tribe Pyreae of Rosaceae. Both yeast two-hybrid and pull-down assays demonstrated that they could connect PbSLFs to PbCUL1 to form a putative canonical SCF^SLF (SSK/CUL1/SLF) complex in Pyrus. Furthermore, pull-down assays showed that the SSK proteins could bind SLF and CUL1 in a cross-species manner between Pyrus and Petunia. Additionally, phylogenetic analysis revealed that the SSK-like proteins from Solanaceae, Plantaginaceae and Rosaceae form a monoclade group, hinting their shared evolutionary origin. Taken together, with the recent identification of a canonical SCF^SFB complex in Prunus of the tribe Amygdaleae of Rosaceae, our results show that a conserved canonical SCF^SLF/SFB complex is present in Solanaceae, Plantaginaceae and Rosaceae, implying that S-RNase-based self-incompatibility shares a similar molecular and biochemical mechanism.     

Identification and genetic diversity of plum cultivars grown in Belarus

A study of the collection of sour cherry, sweet cherry, common plum, diploid and tetraploid types of plums, and apricots grown in Belarus carried out using 20 SSR markers showed that they are characterized by high genetic diversity. Among 106 genotypes, 524 polymorphic alleles were identified. The average number of alleles was 15.4 in common plum samples, 11.3 in diploid and tetraploid plum, 9.3 in sour cherry, 6.0 in apricot, and 4.9 in sweet cherry. The greatest genetic diversity is characteristic of common plum cultivars (PD = 0.811). The genetic diversity decreases as follows: diploid plum (PD = 0.741), sour cherry (PD = 0.721), apricot (PD = 0.673), and sweet cherry (PD = 0.655). Cluster analysis shows that the degree of intraspecific divergence in sour cherry and sweet cherry cultivars is less than that of common plum, diploid plum, and apricot plum. Although apricots and plums belong to the subgenus Prunophora, according to the results of SSR analysis, apricot cultivars form a cluster that is more distant from both Cerasus and Prunophora. A set of seven SSR markers (EMPA001, EMPA005, EMPA018, EMPA026 and BPPCT025, BPPCT026, BPPCT039) was selected for DNA identification of cultivars of sour cherry, sweet cherry, common plum, diploid plum, and apricot, as well as species and interspecies hybrids.     

Molecular typing of the self-incompatibility locus of Turkish sweet cherry genotypes reflects phylogenetic relationships among cherries and other Prunus species

Self-incompatibility of sweet cherry (Prunus avium L.) is controlled by the multiallelic S-locus. While many cultivars and wild accessions have been S-genotyped, only limited data are available on accessions native to the center of origin of this species. Therefore, this study was carried out to determine the S-genotype of 11 landrace cultivars and 17 local genotypes selected from populations growing wild at the Black Sea coast. Eleven sweet cherries (S ₁–S ₇, S ₁₀, and S ₁₂–S ₁₄) and some wild cherries (S ₁₇–S ₁₉, S _21/25, and S ₃₁) S-RNase alleles were detected. The results indicate that Turkish cultivars represent a broader gene pool as compared with international cultivars. A new (S ₃₇) and a doubtful allele (provisionally labelled as S _7m) as well as the sour cherry S ₃₄-allele were identified in sweet cherry. These data and others (SSR variants within the S ₁₃-RNase introns) confirmed that allele pools of sweet and sour cherries in the Black Sea region are overlapping. A new cross-incompatibility group, XLV (S ₂ S ₁₈), was also proposed. Allele-specific primers were designed for S ₁₇–S ₁₉, S _21/25, S ₃₄, and S ₃₇. A phylogenetic analysis of the cherry S ₃₁-RNase and its trans-specific sister alleles reliably mirrored the assumed length of the time period after the divergence of species in the subgenera Cerasus and Prunophora. Most variations (insertions/deletions and single-nucleotide polymorphisms) in the S-RNase gene were silent and, hence, have not been exposed to natural selection. The results are discussed from the aspects of S-allele evolution and phylogenetic relationships among cherries and other Prunus species.     

Mono- and digalactosyldiacylglycerols: potent nitric oxide inhibitors from the marine microalga Nannochloropsis granulata

Chemical investigation of a marine microalga, Nannochloropsis granulata, led to the isolation of four digalactosyldiacylglycerols namely, (2S)-1-O-eicosapentaenoyl-2-O-palmitoyl-3-O-(β-d-galactopyranosyl-6-1α-d-galactopyranosyl)-glycerol (1), (2S)-1-O-eicosapentaenoyl-2-O-palmitoleoyl-3-O-(β-d-galactopyranosyl-6-1α-d-galactopyranosyl)-glycerol (2), (2S)-1-O-eicosapentaenoyl-2-O-myristoyl-3-O-(β-d-galactopyranosyl-6-1α-d-galactopyranosyl)-glycerol (3), and (2S)-1,2-bis-O-eicosapentaenoyl-3-O-(β-d-galactopyranosyl-6-1α-d-galactopyranosyl)-glycerol (4), together with their monogalactosyl analogs (5–8). Among the isolated galactolipids 2 and 3 were new natural products. Complete stereochemistry of 1, 4, 5, 7, and 8 was determined for the first time by both spectroscopic techniques and classical degradation methods. Both mono- and digalactosyldiacylglycerols isolated from N. granulata possessed strong nitric oxide (NO) inhibitory activity against lipopolysaccharide-induced NO production in RAW264.7 macrophage cells through downregulation of inducible nitric oxide synthase expression indicating the possible use as anti-inflammatory agents.     

Molecular and Genetic Analyses of Four Nonfunctional S Haplotype Variants Derived from a Common Ancestral S Haplotype Identified in Sour Cherry (Prunus cerasus L.)

Tetraploid sour cherry (Prunus cerasus) has an S-RNase-based gametophytic self-incompatibility (GSI) system; however, individuals can be either self-incompatible (SI) or self-compatible (SC). Unlike the situation in the Solanaceae, where self-compatibility accompanying polyploidization is often due to the compatibility of heteroallelic pollen, the genotype-dependent loss of SI in sour cherry is due to the compatibility of pollen containing two nonfunctional S haplotypes. Sour cherry individuals with the S₄S₆S_36aS_36b genotype are predicted to be SC, as only pollen containing both nonfunctional S_36a and S_36b haplotypes would be SC. However, we previously found that individuals of this genotype were SI. Here we describe four nonfunctional S₃₆ variants. Our molecular analyses identified a mutation that would confer loss of stylar S function for one of the variants, and two alterations that might cause loss of pollen S function for all four variants. Genetic crosses showed that individuals possessing two nonfunctional S₃₆ haplotypes and two functional S haplotypes have reduced self-fertilization due to a very low frequency of transmission of the one pollen type that would be SC. Our finding that the underlying mechanism limiting successful transmission of genetically compatible gametes does not involve GSI is consistent with our previous genetic model for Prunus in which heteroallelic pollen is incompatible. This provides a unique case in which breakdown of SI does not occur despite the potential to generate SC pollen genotypes.GAMETOPHYTIC self-incompatibility (GSI) is a widespread mechanism in flowering plants that prevents self-fertilization and promotes out-crossing (De Nettancourt 2001). In GSI plants, pollen tube growth is arrested if there is a match between the genes at the S-locus that control pollen and stylar specificity. The gene controlling stylar specificity in the Solanaceae, Rosaceae, and Plantaginaceae is known to encode a ribonuclease (S-RNase) (for a review see McClure 2009), while the gene controlling pollen specificity encodes an F-box protein [S haplotype-specific F-box protein (SFB) or S-locus F-box protein (SLF)] (Lai et al. 2002; Entani et al. 2003; Ushijima et al. 2003; Sijacic et al. 2004). As these two specificity genes are tightly linked and recombination between these two genes has never been observed (Ikeda et al. 2005), these two S-locus specificity genes are collectively termed the S haplotype.Characterization of the S haplotype is most advanced in Prunus (Rosaceae) due to the small physical size of the S haplotype region and the close proximity of the stylar S (S-RNase) and pollen S (SFB) genes (Entani et al. 2003; Ushijima et al. 2003; Yamane et al. 2003b; Ikeda et al. 2005). Within Prunus, sweet cherry (Prunus avium) and sour cherry (P. cerasus) represent a model diploid–tetraploid series that has been used to investigate the effects of polyploidy on GSI. Tetraploid sour cherry is considered to have arisen through hybridization between sweet cherry and tetraploid ground cherry (P. fruticosa) (Olden and Nybom 1968). Like sweet cherry, sour cherry exhibits an S-RNase-based GSI system (Yamane et al. 2001; Hauck et al. 2002; Tobutt et al. 2004) and interspecific crossing studies have demonstrated that sour cherry shares eight sweet cherry S haplotypes: S₁, S₄, S₆, S₉, S₁₂, S₁₃, S₁₄, and S₁₆ (Bošković et al. 2006; Hauck et al. 2006a,b; Tsukamoto et al. 2006, 2008). However, in contrast to sweet cherry, natural sour cherry selections include both self-incompatible (SI) and self-compatible (SC) types. A genetic model demonstrating that the genotype-dependent loss of SI in sour cherry is due to the accumulation of a minimum of two nonfunctional S haploytpes within a single individual was developed and validated (Hauck et al. 2006b). These nonfunctional S haplotypes were characterized as either pollen-part mutants or stylar-part mutants, depending on whether the pollen S or stylar S specificity was disrupted. In Prunus, pollen-part and stylar-part mutants are denoted by a prime symbol “′” or a subscribed “m,” respectively, following the S haplotype number (Tsukamoto et al. 2006). Molecular characterizations of five of the nonfunctional S haplotypes from sour cherry characterized to date support the genetic results because mutations were identified that affected the S-RNase and/or SFB. These changes in coding or regulatory regions included mutations within the S-RNase and/or SFB causing premature stop codons, transposable element insertions within SFB and upstream of the S-RNase, and a 23-bp deletion in a conserved region of the S-RNase (Yamane et al. 2003a; Hauck et al. 2006a; Tsukamoto et al. 2006).According to the genetic model, termed the “one-allele-match model,” sour cherry pollen is rejected if one or both of the functional S haplotypes in the 2x pollen grain match an S haplotype in the style (Hauck et al. 2006b). Therefore, only pollen containing two nonfunctional S haplotypes would be SC; thus, a sour cherry genotype is SC if it has a minimum of two nonfunctional S haplotypes. We previously tested the one-allele-match model using 92 sour cherry selections from four progeny populations (Hauck et al. 2006b). For all the progeny except three, their S genotype correctly predicted whether they were SI or SC. The three progeny individuals that were the exception all had the same genotype: S₄S₆S_aS_d. These individuals were predicted to be SC as the S_a and S_d haplotypes were shown to be nonfunctional in genetic studies and therefore S_aS_d pollen should be SC. However, these progeny were classified as SI on the basis of observations of self-pollen tube growth in the styles. The S_a and S_d haplotypes were originally distinguished on the basis of different RFLP fragment sizes using an S-RNase probe; the HindIII fragment sizes for S_a and S_d differed by ∼200 bp, 6.4-kb and 6.2-kb, respectively (Yamane et al. 2001; Hauck et al. 2002). However, partial S-RNase and SFB sequences from the S_a and S_d haplotypes were identical (N. R. Hauck and A. F. Iezzoni, unpublished results), suggesting that S_a and S_d represented different mutations of the same S haplotype. Therefore, we hypothesized that the SI phenotype of the S₄S₆S_aS_d individuals resulted from complementary pistil S and pollen S mutations in the nonfunctional S_a and S_d haplotypes, thus behaving genetically as one functional S haplotype.We previously reported that heteroallelic sour cherry pollen containing two different functional pollen S haplotypes is incompatible (Hauck et al. 2006b). This finding is counter to the well-documented phenomenon in the Solanaceae where SC accompanying polyploidization is frequently due to the SC of heteroallelic pollen (Lewis 1943; Golz et al. 1999, 2001; Tsukamoto et al. 2005; Xue et al. 2009). Therefore, models explaining the molecular basis of self-recognition in Prunus and the Solanaceae must be consistent with these differing genetic expectations. Recently, Huang et al. (2008) reported competitive interaction in a SC selection of tetraploid P. pseudocerasus, raising the possibility that the SC mechanism between these two tetraploid Prunus species could be different. However, although the data in Huang et al. (2008) are consistent with heteroallelic pollen being SC, homoallelic pollen (e.g., S₁S₁, S₅S₅, or S₇S₇) was not shown to be successful in compatible crosses and unsuccessful in incompatible ones. Therefore, it is possible that the SC in P. pseudocerasus could be caused by mutations in other genes critical for the SI reaction. Because of the importance of these differing genetic expectations for understanding S-RNase-based GSI, we sought to investigate our previously identified exceptions to the one-allele-match model. Specifically, our objective was to test our prior hypothesis that the nonfunctional S_a and S_d haplotypes interact in a complementary manner and therefore behave together genetically as a single functional S haplotype. In this work, the S_a and S_d haplotypes were renamed S_36a and S_36b, respectively, following the order of previously published S haplotypes (Tsukamoto et al. 2008; Vaughan et al. 2008) for reasons explained in the results.     

New diacylglyceryltrimethylhomoserines from the marine microalga Nannochloropsis granulata and their nitric oxide inhibitory activity

Chemical investigation of polar lipids from the marine eustigmatophyte microalga Nannochloropsis granulata led to the isolation of six betaine lipid diacylglyceryltrimethylhomoserine (DGTS), namely, (2S)-1,2-bis-O-eicosapentaenoylglyceryl-3-O-4′-(N,N,N-trimethyl)-homoserine (1), (2S)-1-O-eicosapentaenoyl-2-O-arachidonoylglyceryl-3-O-4′-(N,N,N-trimethyl)-homoserine (2), (2S)-1-O-eicosapentaenoyl-2-O-myristoylglyceryl-3-O-4′-(N,N,N-trimethyl)-homoserine (3), (2S)-1-O-eicosapentaenoyl-2-O-palmitoylglyceryl-3-O-4′-(N,N,N-trimethyl)-homoserine (4), (2S)-1-O-eicosapentaenoyl-2-O-palmitoleoylglyceryl-3-O-4′-(N,N,N-trimethyl)-homoserine (5), and (2S)-1-O-eicosapentaenoyl-2-O-linoleoylglyceryl-3-O-4′-(N,N,N-trimethyl)-homoserine (6). Structures of the isolated DGTSs were elucidated based on both spectroscopic technique and degradation methods. This is the first report of isolation of 1 in pure state, and 2–6 are all new compounds. The isolated betaine lipids showed dose-dependent nitric oxide (NO) inhibitory activity against lipopolysaccharide-induced nitric oxide production in RAW264.7 macrophage cells. Further study suggested that these betaine lipids (1–6) inhibit NO production in RAW264.7 macrophage cells through downregulation of inducible nitric oxide synthase expression, indicating the possible use as an anti-inflammatory agent. This is the first report of DGTS with anti-inflammatory activity.     

Nucleotide sequence analysis of <Emphasis Type="Italic">S</Emphasis>-locus genes to unify <Emphasis Type="Italic">S</Emphasis> haplotype nomenclature in radish

Radish, belonging to the family Brassicaceae, has a self-incompatibility which is controlled by multiple alleles on the S locus. To employ the self-incompatibility in an F₁ breeding system, identification of S haplotypes is necessary. Since collection of S haplotypes and determination of nucleotide sequences of SLG, SRK, and SCR alleles in cultivated radish have been conducted by different groups independently, the same or similar sequences with different S haplotype names and different sequences with the same S haplotype names have been registered in public databases, resulting in confusion of S haplotype names for researchers and breeders. In the present study, we developed S homozygous lines from radish F₁ hybrid cultivars in Japan and determined the nucleotide sequences of SCR, the S domain and the kinase domain of SRK, and the SLG of a large number of S haplotypes. Comparing these sequences with our previously published sequences, the haplotypes were ordered into 23 different S haplotypes. The sequences of the 23 S haplotypes were compared with S haplotype sequences registered by different groups, and we suggested a unification of these S haplotypes. Furthermore, dot-blot hybridization using SRK allele-specific probes was examined for developing a standard method for S haplotype identification.     

Cloning of seed dormancy genes (TaSdr) associated with tolerance to pre-harvest sprouting in common wheat and development of a functional marker

Key message

After cloning and mapping of wheat TaSdr genes, both the functional markers for TaSdr - B1 and TaVp - 1B were validated, and the distribution of allelic variations at TaSdr - B1 locus in the wheat cultivars from 19 countries was characterized.

Abstract

Seed dormancy is a major factor associated with pre-harvest sprouting (PHS) in common wheat (Triticum aestivum L.). Wheat TaSdr genes, orthologs of OsSdr4 conferring seed dormancy in rice, were cloned by a comparative genomics approach. They were located on homoeologous group 2 chromosomes, and designated as TaSdr-A1, TaSdr-B1 and TaSdr-D1, respectively. Sequence analysis of TaSdr-B1 revealed a SNP at the position -11 upstream of the initiation codon, with bases A and G in cultivars with low and high germination indices (GI), respectively. A cleaved amplified polymorphism sequence marker Sdr2B was developed based on the SNP, and subsequently functional analysis of TaSdr-B1 was conducted by association and linkage mapping. A QTL for GI co-segregating with Sdr2B explained 6.4, 7.8 and 8.7 % of the phenotypic variances in a RIL population derived from Yangxiaomai/Zhongyou 9507 grown in Shijiazhuang, Beijing and the averaged data from those environments, respectively. Two sets of Chinese wheat cultivars were used for association mapping, and results indicated that TaSdr-B1 was significantly associated with GI. Analysis of the allelic distribution at the TaSdr-B1 locus showed that the frequencies of TaSdr-B1a associated with a lower GI were high in cultivars from Japan, Australia, Argentina, and the Middle and Lower Yangtze Valley Winter Wheat Region and Southwest Winter Wheat Region in China. This study provides not only a reliable functional marker for molecular-assisted selection of PHS in wheat breeding programs, but also gives novel information for a comprehensive understanding of seed dormancy.     

An efficient lipase-catalyzed enantioselective hydrolysis of (R,S)-azolides derived from N-protected proline, pipecolic acid, and nipecotic acid

In the Candida antarctica lipase B-catalyzed hydrolysis of (R,S)-azolides derived from (R,S)-N-protected proline in water-saturated methyl tert-butyl ether (MTBE), high enzyme activity with excellent enantioselectivity (V _S V _R ^?1 ?>?100) for (R,S)-N-Cbz-proline 1,2,4-triazolide (1) and (R,S)-N-Cbz-proline 4-bromopyrazolide (2) was exploited in comparison with their corresponding methyl ester analog (3). Changing of the substrate structure, water content, solvent, and temperature was found to have profound influences on the lipase performance. On the basis of enzyme activity and enantioselectivity and solvent boiling point, the best reaction condition of using 1 as the substrate in water-saturated MTBE at 45 °C was selected and further employed for the successful resolution of (R,S)-N-Cbz-pipecolic 1,2,4-triazolide (5) and (R,S)-N-Boc-nipecotic 1,2,4-triazolide (9). Moreover, more than 89.1 % recovery of remained (R)-1 is obtainable in five cycles of enzyme reusage, when pH 7 phosphate buffers were employed as the extract at 4 °C.     

Lipids isolated from the cultivated red alga Chondrus crispus inhibit nitric oxide production

A MeOH extract of cultivated Chondrus crispus showed dose-dependent nitric oxide (NO) inhibition of lipopolysaccharide-induced NO production in macrophage RAW264.7 cells. NO inhibition-guided fractionation of the extract led to identification of eicosapentaenoic acid (EPA, 1), arachidonic acid (AA, 2), lutein (3), and eight galactolipids as active components. Based on spectral analysis, the isolated galactolipids were identified as (2S)-1,2-bis-O-eicosapentaenoyl-3-O-β-d-galactopyranosylglycerol (4), (2S)-1-O-eicosapentaenoyl-2-O-arachidonoyl-3-O-β-d-galactopyranosylglycerol (5), (2S)-1-O-(6Z,9Z,12Z,15Z-octadecatetranoyl)-2-O-palmitoyl-3-O-β-d-galactopyranosylglycerol (6), (2S)-1-O-eicosapentaenoyl-2-O-palmitoyl-3-O-β-d-galactopyranosylglycerol (7), (2S)-1,2-bis-O-arachidonoyl-3-O-β-d-galactopyranosylglycerol (8), (2S)-1-O-arachidonoyl-2-O-palmitoyl-3-O-β-d-galactopyranosylglycerol (9), (2S)-1-O-eicosapentaenoyl-2-O-palmitoyl-3-O-(β-d-galactopyranosyl-6-1α-d-galactopyranosyl)-glycerol (10), and (2S)-1-O-arachidonoyl-2-O-palmitoyl-3-O-(β-d-galactopyranosyl-6-1α-d-galactopyranosyl)-glycerol (11). All the isolated compounds showed significant NO inhibitory activity. This is the first report of the isolation and identification of individual galactolipids from C. crispus. Moreover, (2S)-1,2-bis-O-arachidonoyl ?3-O-β-d-galactopyranosylglycerol (8) is a novel compound.     

Five new galactolipids from the freshwater microalga Porphyridium aerugineum and their nitric oxide inhibitory activity

Chemical investigation of the freshwater rhodophyte microalga Porphyridium aerugineum led to the isolation of five new galactolipids, namely, (2S)-1-O-eicosapentaenoyl-2-O-arachidonoyl-3-O-β-d-galactopyranosylglycerol (1), (2S)-1-O-eicosapentaenoyl-2-O-linoleoyl-3-O-β-d-galactopyranosylglycerol (2), (2S)-1-O-arachidoyl-2-O-palmitoyl-3-O-(β-d-galactopyranosyl-6-1α-d-galactopyranosyl)-glycerol (6), (2S)-1-O-eicosapentaenoyl-2-O-arachidoyl-3-O-(β-d-galactopyranosyl-6-1α-d-galactopyranosyl)-glycerol (7), and (2S)-1-O-eicosapentaenoyl-2-O-linoleoyl-3-O-(β-d-galactopyranosyl-6-1α-d-galactopyranosyl)-glycerol (8) together with five known galactolipids. The stereo-structures of all new galactolipids were elucidated by spectroscopic analyses and both enzymatic and chemical degradation methods. This is the first report of galactolipids from P. aerugineum. The newly isolated galactolipids showed strong and dose-dependent nitric oxide (NO) inhibitory activity against lipopolysaccharide-induced NO production in RAW264.7 macrophage cells. Both galactolipids 1 and 2 possessed stronger NO inhibitory activity than N ^G-methyl-l-arginine acetate salt, a well-known NO inhibitor used as a positive control. Further study suggested that these galactolipids inhibit NO production through downregulation of inducible nitric oxide synthase expression.     

Two novel hydroperoxylated products of 20(S)-protopanaxadiol produced by Mucor racemosus and their cytotoxic activities against human prostate cancer cells

Microbial transformation of 20(S)-protopanaxadiol (1) by Mucor racemosus AS 3.205 yielded two novel hydroperoxylated metabolites and three known hydroxylated metabolites. The structures of the metabolites were identified as 26-hydroxyl-20(S)-protopanaxadiol (2), 23,24-en-25-hydroxyl-20(S)-protopanaxadiol (3), 25,26-en-24(R)-hydroperoxyl-20(S)-protopanaxadiol (4), 23,24-en-25-hydroperoxyl-20(S)-protopanaxadiol (5), and 25-hydroxyl-20(S)-protopanaxadiol (6). 4 and 5 are new compounds. Metabolites 2, 4, and 5 showed the more potent inhibitory effects against DU-145 and PC-3 cell lines than the substrate.     

Microbial transformation of 20(S)-protopanaxatriol by Absidia corymbifera and their cytotoxic activities against two human prostate cancer cell lines

Seven hydroxylates of 20(S)-protopanaxatriol (1) transformed by Absidia corymbifera AS 3.3387 were isolated and identified by spectral methods including 2D-NMR. Among them, 7β-hydroxyl-20(S)-protopanaxatriol (2), 7α-hydroxyl-20(S)-protopanaxatriol (3), and 7β, 15α-dihydroxyl-20(S)-protopanaxatriol (7) are new compounds. The metabolites 2, 6, 7, and 8 showed the more potent inhibitory effects against DU-145 and PC-3 cell lines than the substrate.     

Density functional studies on photophysical properties and chemical reactivities of the triarylboranes: effect of the constraint of planarity

The geometric and electronic structures, absorption spectra, transporting properties, chemical reactivity indices and electrostatic potentials of the planar three-coordinate organoboron compounds 1-2 and twisted reference compound Mes ₃ B, have been investigated by employing density functional theory (DFT) and conceptual DFT methods to shed light on the planarity effects on the photophysical properties and the chemical reactivity. The results show that the planar compounds 1-2 exhibit significantly lower HOMO level than Mes ₃ B, owing to the stronger electronic induction effect of boron centers. This feature conspicuously induces a blue shifted absorption for 1, although 1 seemingly possesses more extended conjugation framework than Mes ₃ B. Importantly, the reactivity strength of the boron atoms in 1-2 is much lower than that in Mes ₃ B, despite the fact that the tri-coordinate boron centers of 1-2 are completely naked. The interesting and abnormal phenomenon is caused by the strong p-π electronic interactions, that is, the empty p-orbital of boron center is partly filled by π-electron of the neighbor carbon atoms in 1-2, which are confirmed by the analysis of Laplacian of the electron density and natural bond orbitals. Furthermore, the negative electrostatic potentials of the boron centers in 1-2 also interpret that they are not the most preferred sites for incoming nucleophiles. Moreover, it is also found that the planar compounds 1-2 can act as promising electron transporting materials since the internal reorganization energies for electron are really small.

Oxygenated verticillene derivatives from Bursera suntui

Medium polarity fractions of the hexane extracts of the stems of Bursera suntui afforded six previously known (1-6) and four hitherto unknown verticillane derivatives: (1S,3Z,7S,8S,11S,12S)-(+)-7,8-epoxyverticill-3-en-12,20-diol (7), (1S,3Z,7S,8S,11S,12S)-(+)-7,8-epoxyverticill-3-en-12,20-diol 20-acetate (8), (1S,3Z,7S,11S,12S)-(+)-verticilla-3,8(19)-dien-7,12,20-triol (9), and (1S,3Z,7S,11S,12S)-(+)-verticilla-3,8(19)-dien-7,12,20-triol 20-acetate (10). Acetylation of 9 and 10 yielded (1S,3Z,7S,11S,12S)-(+)-verticilla-3,8(19)-dien-7,12,20-triol 7,20-diacetate (11), while hydrolysis of 8 gave 7. The structures and stereochemistry of 7-11 were established by spectroscopic analyses, particularly by 1D and 2D NMR spectra and HRESIMS. The conformational preferences of 7-11 were studied by molecular mechanics modelling employing the Monte Carlo protocol followed by B3LYP/DGDZVP DFT calculation, thus supporting the observed ¹H NMR NOESY cross peaks.