Two new pentacyclic triterpenoids from Lantana camara LINN

Two new pentacyclic triterpenoids, namely lantanoic acid (1) and camaranoic acid (2), and six known compounds such as lantic acid, camarinic acid, camangeloyl acid, camarinin, oleanonic acid, and ursonic acid were isolated from the aerial parts of Lantana camara LINN. Structures of the new constituents were elucidated by chemical transformation and spectral studies including 1D ((1)H- and (13)C-NMR) and 2D ((1)H-(1)H correlation spectroscopy (COSY), nuclear Overhauser effect spectroscopy (NOESY), (1)H-(1)H total correlation spectroscopy (TOCSY), J-resolved, (1)H-detected heteronuclear multiple quantum coherence (HMQC), and heteronuclear multiple bond connectivity (HMBC)) NMR spectroscopy.     

The length of esterifying alcohol affects the aggregation properties of chlorosomal bacteriochlorophylls

Abstract Chlorosomes, the main light-harvesting complexes of green photosynthetic bacteria, contain bacteriochlorophyll (BChl) molecules in the form of self-assembling aggregates. To study the role of esterifying alcohols in BChl aggregation we have prepared a series of bacteriochlorophyllide c (BChlide c) derivatives differing in the length of the esterifying alcohol (C(1), C(4), C(8) and C(12)). Their aggregation behavior was studied both in polar (aqueous buffer) and nonpolar (hexane) environments and the esterifying alcohols were found to play an essential role. In aqueous buffer, hydrophobic interactions among esterifying alcohols drive BChlide c derivatives with longer chains into the formation of dimers, while this interaction is weak for BChlides with shorter esterifying alcohols and they remain mainly as monomers. All studied BChlide c derivatives form aggregates in hexane, but the process slows down with longer esterifying alcohols due to competing hydrophobic interactions with hexane molecules. In addition, the effect of the length of the solvent molecules (n-alkanes) was explored for BChl c aggregation. With an increasing length of n-alkane molecules, the hydrophobic interaction with the farnesyl chain becomes stronger, leading to a slower aggregation rate. The results show that the hydrophobic interaction is the driving force for the aggregation in an aqueous environment, while in nonpolar solvents it is the hydrophilic interaction.     

Antimicrobial activity of the methanolic bark extract of Holarrhena pubescens (Buch. Ham), its fractions and the pure compound conessine

The antimicrobial activity of the methanolic extract of the bark of Holarrhena pubescens, its fractions, and conessine, a steroidal alkaloid, was determined against various bacteria and fungi using the agar diffusion method. They were all found to possess significant activity against some of the bacteria tested. The alkaloidal fraction and conessine also exhibited marginal activity against some of the fungi tested. The minimum inhibitory concentration (MIC) value of conessine was determined against various bacteria, and the highest activity was seen against Micrococcus luteus ATCC 9341 (MIC: 15.6?μg per disc).     

Antimycobacterial and antioxidant activities of reserpine and its derivatives

In view of the attributed medicinal properties of reserpine, a number of acyl reserpine derivatives were prepared and tested for antimycobacterial activity against Mycobacterium tuberculosis, strain H(37)Rv and antioxidant activities. The results indicated that in the case of antimycobacterial activity, 10 out of 18 derivatives caused more inhibition than that caused by reserpine itself. The results of antioxidant activity revealed that acylation in benzene ring of reserpine decreases the percentage inhibition of DPPH in all the derivatives compared to the parent compound (1).     

A new tetracyclic triterpenoid from the leaves of Azadirachta indica

A new tetracyclic triterpenoid zeeshanol [25,26,27-trinor-apotirucalla-(apoeupha)-6alpha-, 21-dihydroxy, 7alpha-acetoxy, 1,14,22-tri-en-3, 16-dione] (1) along with a known constituent desfurano-6alpha-hydroxyazadiradione (2) have been isolated from the methanolic extract of the leaves of Azadirachta indica. The structure and the relative configurations of 1 were determined by the spectroscopic method (1H- and 13C-NMR, IR, and MS) and 2D-NMR experiments.     

Studies on the chemical constituents of the fruits of Cordia latifolia

Four new aromatic compounds have been isolated from the fruits of Cordia latifolia (Boreginaceae) bearing a common basic skeleton but differing in the side chain. Their structures were elucidated using spectrometric methods including 1D- (1H and 13C) and 2D-NMR experiments, (1H, 1H-COSY, NOESY, HMQC and HMBC) and chemical transformations.     

Synthesis and Crystal Structure of Bis[O,O'-di(2-phenylethyl)dithiophosphato](α,α'-bipyridine)copper(Ⅱ)

A ternary adduct Cu[S2P(OCH2CH2Ph)2]2·bipy(bipy=α,α'-bipyridine) was syn-thesized and characterized by elemental analysis,IR and single-crystal X-ray diffraction.The crystal belongs to the triclinic system,space group P1 with a=10.2320(2),b=11.5249(3),c=18.0916(3),α=98.95(1),β =103.601(1),γ=91.272(2)°,V=2044.49(7)3,Z=2,Dc=1.453 g/cm3,T=153(2) K,C42H44CuN2O4P2S4,Mr=894.51,λ(MoKα)=0.71073,μ=0.86 mm-1,S=0.999,(△/σ)max=0.002,the final R=0.0243 and wR=0.0704.A total of 9221 unique reflections were collected,of which 8573 with Ⅰ 2σ(Ⅰ) were observed.The Cu(Ⅱ) atom is five-coordinated in a rather distorted trigonal bipyramidal geometry(τ value=0.537).The Cu-S distances range from 2.3491(4) to 2.4829(4) ,and the Cu-N distances are 1.9987(12) and 2.0584(11) ,respectively.An interesting feature of this adduct resides in its two-dimensional(2D) open framework constructing through hydrogen bonding and π-π interactions.     

芴-硫芴共聚物的电子结构和光谱性质的理论研究

用DFT-B3LYP方法对低聚物(PF30T)_n [n(芴)∶n(硫芴)＝2∶1, 物质的量之比, n＝1～4], (PF50T)_n [n(芴)∶n(硫芴)＝1∶1, 物质的量之比, n＝1～4]体系全优化, 得到两系列低聚物的电离能(IP_(a,v))、电子亲和势(EA_(a,v))、空穴抽取能(HEP)、电子抽取能(EEP). 在此基础上用ZINDO和TD-DFT方法计算吸收光谱, 分析了两个系列的HOMO-LUMO能隙随着n递增的变化趋势及硫芴含量对低聚物电子结构和光谱性质的影响, 推断了高聚物的电子和光谱性质. 用ab initio CIS方法优化了低聚物的S₁激发态结构并分析了其与发射光谱的关系. 研究显示: 2,8位引入的硫芴基团, 破坏了链的共轭, 而且随着硫芴含量的增加, HOMO-LUMO能隙变大, 光谱蓝移; 激发态结构趋于共面化.