Two New Species of the Genus Dictyota (Phaeophyceae: Dictyotales) from the Mexican Caribbean

During a molecular characterization of the genus Dictyota J. V. Lamouroux (Phaeophyceae, Dictyotales) along the Mexican coasts of the Gulf of Mexico and the Mexican Caribbean, using psbA and cox1 genes, it was found that two particular collections did not match with the sequences published for a total of 39 species of Dictyota. For each gene, both collections diverged in high-uncorrected “p” distance values with respect to other related species. This high genetic divergence was corroborated by morphological analysis. Hence, we proposed Dictyota mayae J. Lozano-Orozco & Sentíes and Dictyota pedrochei J. Lozano-Orozco & Sentíes as new species.

A NEW DOLASTANE DITERPENE PROM DICTYOTA DIVARICATA

Deacetylamijidictyol, a new dolastane diterpene was isolated from the marine brown algae Dictyota divaricata. The chemical structure was elucidated on the basis of spectral analysis.

Theoretical Study on the Structures,Spectral Properties,and Drugability of Xenicane-type Diterpenoids from Dictyota dichotoma

There are few reports on the relationship between the biological activity and structure of secondary metabolites from Dictyota dichotoma. In this work, the geometric and electronic structures, infrared spectra, ultraviolet spectra, 13C and 1H NMR spectra of 16 xenicane-type diterpenoids extracted from Dictyota dichotoma were studied by the density functional theory ωB97XD/6-311+G(2d,p) method. The analysis of the reactivity indices was carried out via the conceptual density functional theory. Furthermore, a pharmacodynamic evaluation was performed using ADME/Tox. The geometric structure analysis found that all 16 diterpenoids had the same unsaturated, branched chains and could be divided into two categories according to the ring size, including nine-membered and eight-membered rings. A hydroxyl group on the lactone ring reduced the stability of the compound. In contrast, a hydroxyl group on the parent ring had little effect on the compound's stability. The electrostatic potential results preliminarily predicted active sites for nucleophilic/electrophilic reactions. The fitting results of infrared and nuclear magnetic resonance(NMR) data showed that the theoretical values obtained by this method were consistent with the experimental values. The UV-visible absorption spectra showed that the solvent effects caused different redshifts of the absorption peaks. The absorption strength was enhanced. The sixteen diterpenoids displayed a strong absorption peak in the range of 180―200 nm, but the compound containing a carbonyl group presents a weaker absorption peak in the field of 200―240 nm. Compounds 9―11, 14, and 15 have better stability and reactivity with lower chemical potentials and higher electronegativity, electrophilic index, and hardness values. The local reactivity descriptors further identified nucleophilic/electrophilic reaction sites for the sixteen compounds. Finally, the pharmacodynamic evaluation results predicted that compounds 2, 4, 8, 11, and 14―16 have optimal drugability. The theoretical results of this work may provide a rich data information for the other experimental study on the cembrane diterpenoids in medicine.

Antibacterial,cytotoxic and larvicidal potential of Dictyota bartayresiana Lamour

Objective:To reveal the antibacterial,cytotoxic and larvicidal activity of Dictyota bartayresiana Lamour(D.bartayresiana).Methods:Phytochemical analysis of various extracts of D.bartayresiana was performed.The antibacterial activity of D.bartayresiana was evaluated by agar diffusion method.The larvicidal activity of crude extract was evaluated as per the protocol described by World Health Organization.The evaluation of LC_(50) value was carried out after 24 h by probit analysis.Cytotoxicity test was carried out using the standard procedure.The LC_(50) and LC_(90) values were obtained from the best-fit line plotted concentration verses percentage lethality.Results:Phytochemical analysis of various extracts of D.bartayresiana showed the presence of steroids,alkaloids,phenolic groups,cardiac glycosides,flavonoids,saponins,tannins and amino acids.It was observed that the methanolic extracts of D.bartayresiana expressed maximum zone of inhibition against Escherichia coli[(9.4±0.2)mm].Crude methanolic extracts of D.bartayresiana showed the highest larval mortality(LC_(50)=166.33 mg/L and LC_(90)=265.69 mg/L)against Culex quinquefasciatus.Similarly,methanolic extracts of D.bartayresiana displayed the highest cytotoxicity with LC_(50) and LC_(90) values at 202.63 and 354.24 mg/L respectively against Artemia salina.Conclusions:The present results revealed the biopotentials of D.bartayresiana and further investigations are needed to elucidate the active principle.

Bio-potency of Dictyota ciliata J.Agardh

Objective:To reveal the antibacterial,cytotoxicity,larvicidal potentials of Dictyota ciliata J.Agardh(D.ciliata).Methods:Phytochemical,antibacterial screening,cytotoxicity and larvicidal properties of the D.ciliata extracts were carried out according to standard methods.Cytotoxicity and larvicidal potentials were analyzed by means of computerized probit analysis program.Results:The phytochemical screening showed the presence of steroids,alkaloids,phenolic groups,cardiac glycosides,flavonoids and tannins in the crude extracts of D.ciliata.The methanolic extracts of D.ciliata showed the highest metabolites presence compared to other tested extracts.The antibacterial activity illustrated that the acetone extracts of D.ciliata exhibited the highest zone of inhibition[(10±0.2)mm]against Morganella morganii.Highest larval mortality(50%)was observed in the crude methanolic extracts of D.ciliata against Culex quinquefasciatus(LC_(50)=202.82 mg/L and LC_(90) value is 488.52 mg/L).The result of brine shrimp lethality bioassay showed highest cytotoxicity in methanolic extracts of D.ciliata with LC_(50) and LC_(90) values at 340.14 mg/L and 555.58 mg/L respectively.Conclusions:The results of the present phytochemical analysis and biological assays will help the manufacturers for identification and selection of raw materials for drug production.

网地藻多糖清除DPPH·自由基活性的动力学研究

该研究通过超声辅助并采用醇沉、脱蛋白、脱色、干燥的方法,分别检测低(0.1 mg·mL^(-1))、中(0.25mg·mL^(-1))、高(0.5 mg·mL^(-1))三种浓度下的网地藻多糖对DPPH·自由基的清除能力,探讨质量浓度和反应时间对网地藻多糖清除DPPH·自由基活性的变化规律。按照一级反应动力学方程和二级反应动力学方程分别建立反应动力学模型。结果表明:不同的质量浓度和反应时间对网地藻多糖清除DPPH·自由基活性均有影响,网地藻多糖质量浓度提高,其清除DPPH·自由基的能力逐渐加强,当网地藻多糖浓度为0.5 mg·mL^(-1)时,反应20 min,网地藻多糖清除DPPH·自由基的清除率最高为86.06%,其清除DPPH·自由基活性半数清除率(IC_(50))为0.25 mg·mL^(-1)。准一级动力学模型拟合的线性相关性较差,相关系数R^2的范围分别为0.848~0.891;准二级动力学模型拟合的相关系数R^2的范围为0.902~0.967,因此采用二级动力学拟合方程能较好地描述网地藻多糖对DPPH·自由基的清除能力。网地藻多糖在低(0.1 mg·mL^(-1))、中(0.25 mg·mL^(-1))、高(0.5 mg·mL^(-1))三种浓度时对DPPH·的二级反应的清除速率常数(k_2)分别为0.011、0.054、0.421。这说明网地藻多糖随着反应浓度逐渐升高其清除DPPH·自由基的速度越来越快,清除自由基能力也越来越强,结合IC_(50)值来共同评价抗氧化能力,IC_(50)值越小,反应速率值越大,表明其抗氧化活性越好,这与实验得出的数据一致。

湛江海域6种常见经济海藻的营养成分分析

分析采自湛江海域的粗枝软骨藻Chondria crassicaulis、日本沙菜Hypnea japonica、鱼栖菜Acanthophora sp、芋根江蓠Gracilaria blodgettii、平卧松藻Codium repens、网地藻Dictyota dichotoma等6种经济海藻的营养成分。结果表明:碳水化合物是这些海藻的主要营养成分,占藻体干重的42.81%～66.11%,平均为55.93%;粗蛋白含量6.63%～11.13%;粗脂肪含量最低,除网地藻D.dichotoma(2.85%)外,其余5种皆不足藻体干重的1%;粗纤维和灰分含量在种间差别较大;矿物质含量丰富,其中磷、铁和锌分别在平卧松藻C.repens、网地藻D.dichotoma和鱼栖菜Acanthophora中占藻体干重的0.093%、0.13%和0.0055%;氨基酸含量较高,其中Thr、Val、Ile、Leu、Phe几种必需氨基酸的含量均高于FAO标准;不少种类中汞、镉、铅、砷等含量超出我国食品卫生标准。海藻体内的营养成分含量因海藻种类和生长海域的不同而有差异。

网地藻多糖对α-葡萄糖苷酶体外抑制作用的研究

研究网地藻多糖对α-葡萄糖苷酶活性的抑制作用。以网地藻为原料,采用超声辅助水提、醇沉、脱色、脱蛋白、干燥后制得网地藻多糖。利用对-硝基苯酚-α-D-葡萄糖苷(p-nitrophenyl-α-D-glucopyranoside,PNPG)为底物建立酶-抑制剂体外模型,采用双倒数作图法确定其抑制类型。结果表明:网地藻多糖抑制α-葡萄糖苷酶活性的大小会受到反应pH值、反应温度、反应时间及网地藻多糖质量浓度的影响,在反应pH值为6.8、反应温度为37℃、反应时间为20 min的条件下网地藻多糖对α-葡萄糖苷酶具有一定的抑制作用,其IC50为22.64 mg/mL。抑制动力学试验表明网地藻多糖对α-葡萄糖苷酶的抑制作用为混合型抑制。结果表明网地藻多糖具有一定的降糖作用。

中国顶丝藻科新记录Ⅳ

继续报导中国顶丝藻科新记录６种。柏桉旋体藻Ａｕｄｏｕｉｎｅｌａｂｏｎｎｅｍａｉｓｏｎｉａｅ，网地旋体藻Ａ．ｄｉｃｔｙｏｔａｅ，德氏旋体藻Ａ．ｄｒｅｗｉ，网状旋体藻Ａ．ｎｅｔｒｏｃａｒｐａ，太平洋旋体藻Ａ．ｐａｃｉｌｉｃａ，异形旋体藻Ａ．ｖａｇａ。

柱前衍生HPLC法分析网地藻多糖的单糖组成

目的:建立测定网地藻多糖的单糖组成方法。方法:采用超声辅助提取、乙醇沉淀、Sevage法脱蛋白制备网地藻多糖,采用硫酸水解后,水解产物以1-苯基-3-甲基-5-吡唑酮(PMP)柱前衍生化后采用反相高效液相色谱法于248 nm处测定单糖组成。色谱柱为Diamonsil C18(250mm×4.6 mm,5μm);流动相为0.02 mol/L磷酸缓冲盐(A)-乙腈(B),洗脱梯度(0 min,0%B;10min,18%B;25 min,25%B;30 min,30%B)。结果:网地藻多糖含有甘露糖、核糖、鼠李糖、葡萄糖、半乳糖和木糖,其摩尔比为0.24:0.04:0.03:1:0.19:0.1。结论:该方法准确可靠、分离效果较好,可用于网地藻多糖的单糖组成测定。