Flavonoid aglycones from leaf resins of two species of Heterotheca (compositae)

Twenty-nine flavonoid aglycones have been identified from two populations each of Heterotheca grandiflora and H. psammophila. Considerable qualitative variation was found between populations of the same species. Overall, H. grandiflora is more complex in its flavonoid profile, accumulating a total of 24 compounds based on eight skeletal types, compared with 13 compounds based on four skeletal types in H. psammophila.     

中国锦葵科一新记录种——克氏梧桐

首次报道中国锦葵科一新记录种——克氏梧桐［Firmiana kerrii (Craib) Kosterm.］。该种原记载产自泰国和缅甸,2019年该种在中国云南西双版纳州勐腊县发现有分布。凭证标本保存在中国科学院西双版纳热带植物园标本馆(HITBC)。该文给出了中国已知的9种梧桐属植物的分种检索表。     

Flavonoids from chemotypes of the goldback fern, Pityrogramma triangularis

More than 20 flavonoid aglycones were identified from the frond exudate of various collections of Pityrogramma triangularis. Ten of them are novel natural products; most of the others are rare flavonoids. They are substituted at C-8; many are C-methylated. They mostly occur only as trace constituents in var. triangularis. Two compounds come from var. viscosa. One population of P. triangularis var. triangularis exhibits a unique flavonoid pattern not encountered before in any other chemotype studied.     

中国锦葵科一新记录属——沙稔属

报道了中国锦葵科（Malvaceae）一新记录属——沙稔属（Sidastrum Baker f.）,小花沙稔[Sidastrum micranthum （A. St.-Hil.）Fryxell]首次在广东发现。     

Exudate flavonoid aglycones of Veronica: Ecological and systematic implications

A survey on the distribution of surface flavonoid aglycones in 52 samples of 29 species of Veronica resulted in detection of eight flavone aglycones. Apigenin and luteolin were the most common constituents of the studied exudates, followed by the methylated derivatives apigenin 4′-methyl ether, apigenin 7,4′-dimethyl ether and luteolin 3′-methyl ether. Some intraspecific variations and the main ecological trends of flavonoid aglycone accumulation in Veronica were discussed. The observed exudate profiles appeared to be characteristic for some related groups within the genus, in agreement with the morphological, karyological, molecular and other chemical data.     

Lipophilic Phenolics from the Leaves of Empetrum nigrum — Chemical Structures and Exudate Localization

In the course of continuing studies on the occurrence and chemical composition of lipophilic exudates on plant surfaces, the leaves of Empetrum nigrum have been studied. They were found to produce a considerable amount of lipophilic material which mostly consists of phenolic compounds. We here report the identification of two dioxygenated chalcones, three dioxygenated dihydrochalcones, and two dihydrophenanthrene derivatives. Exept for one chalcone, all these compounds were found for the first time as natural products. The upper and lower epidermis of the rolled hypostomatous leaves bear glandular trichomes. By flavonoid specific staining it can be shown that these natural products are accumulated within the capitate glandular cells.     

Delayed autonomous self-pollination in Hibiscus laevis (Malvaceae)

Delayed autonomous self-pollination allows outcrossing to occur while also ensuring that seeds are produced in the absence of pollen vectors. We investigated variation in the efficacy of this pollination mechanism in populations of Hibiscus laevis. Recurvature of stylar branches occurred after 1 d of anthesis, and in plants from Ohio, Illinois, Arkansas, and Oklahoma this behavior resulted in autonomous selfing (surprisingly, stylar movement was facultative in that it did not take place when the stigmas were already pollinated). In contrast to these more northern populations, the distance between anthers and stigmas was too great to allow autonomous selfing in plants from Texas, Mississippi, and Louisiana. Greenhouse studies of plants from Ohio demonstrated that autonomous selfing resulted in an average of 29.5 seeds per flower, as compared to 59.9 seeds per flower from hand-pollination of stigmas with self pollen. In an assessment of the possible significance of this selfing mode, emasculated flowers did not set significantly fewer seeds in a natural stand in Ohio, suggesting that few seeds resulted from autonomous selfing at that site. Modest inbreeding depression was detected at this population. Our results suggest that delayed autonomous selfing is more common in northern populations, where it may facilitate population establishment and persistence at times when pollinators are scarce.     

Prenylated flavonoids from the aerial parts of Dorstenia mannii

Four new prenylated flavanones, dorsmanins 1, J and epi-dorsmanins F, G, identified, respectively, as 6,7-(2,2-dimethylpyrano)-8-prenyl-5,3',4'-trihydroxyflavanone, 6,7-(2,2-dimethyldihydropyrano)-8-prenyl-5,3',4'-trihydroxflavanone, and 2'-epimers of dorsmanins F and G were isolated from the aerial parts of Dorstenia mannii together with 13 known flavonoids: 4-hydroxylonchocarpin, 4-methoxylonchocarpin, 6-prenylchrysoeriol, 6,8-diprenyleriodictyol, gancaonin P and dorsmanins A-H. The structures of these secondary metabolites were determined by spectroscopic means and by comparison with published data and with authentic specimens for some of the known compounds.     

大萼香茶菜中的二萜化学成分研究

为研究大萼香茶菜(Isodon macrocalyx )的化学成分,该文采用硅胶、ODS、Sephadex LH-20、反相C₁₈半制备高效液相等色谱方法对大萼香茶菜地上部分进行分离纯化,并利用¹H NMR、¹³C NMR和HR-ESI-MS等波谱数据,以及结合 参考文献,鉴定了这些化合物的结构。结果表明:从大萼香茶菜地上部分分离得到13个二萜,它们分别是19-羟基陶塔酚(1)、macrophynin E(2)、inumakoic acid(3)、inumakiol D(4)、4β-carboxy-19-nortotarol(5)、(-)-lambertic acid(6)、2-oxo-5-fagonene(7)、isodoterniofiln B(8)、长管贝壳杉素E(9)、长管香茶菜素A(10)、牛尾草素H(11)、16S-dihydrolongikaurin A(12)和ent-3S,16S,17-trihydroxy-kauran-2-one(13)。所有得到的二萜均为首次从该植物中分离得到。     

Flavonoids in the leaves of Thymus: a chemotaxonomic survey

The flavonoid aglycone analysis of 20 Thymus taxa (most Iberic or Balearic endemics) shows the presence of luteolin, apigenin, acacetin, genkwanin, 6-hydroxyluteolin, xanthomicrol, cirsimaritin; four partially identified flavones, of which three are 6-OR-substituted and one flavonol. The differences observed between T. capitatus (L.) Hoffmanns. et Link (subgenus Coridothymus (Reichenb. fil.) Borbás) and the other species belonging to the subgenus Thymus (L.) Jalas, seem enough to maintain the separation of the two groups, but within the same genus, as proposed in Flora Europaea.     

油樟叶中黄酮类物质抑菌效果研究

探究从油樟（Cinnamomum longipaniculatum）叶中提取出的不同极性黄酮样品对大肠杆菌（Escherichia coli）、志贺杆菌（Shigella）、金黄色葡萄球菌（Staphylococcus aureus）、稻瘟病菌（Magnaporthe grisea）和黄曲霉菌（Aspergillus flavus）五种病原菌的抑制作用。以五种病原菌为指示菌,将不同的黄酮样品滴加在滤纸片上,观察抑菌圈的大小。结果显示,样品Fr1、Fr2、Fr3、Fr4和Fr7对大肠杆菌有抑菌作用;样品Fr2、Fr3、Fr4、Fr5、Fr7和Fr8对志贺杆菌有抑菌作用;样品Fr4和Fr8对金黄色葡萄球菌有抑菌作用;样品过孔和Fr4对黄曲霉菌有抑菌作用;样品过孔对稻瘟病菌有抑菌作用。故不同极性的黄酮样品有良好的抑菌性。     

Antioxidant activity-guided isolation of flavonoids from Silene gallica aerial parts

A bio-guided fractionation of the 80% aqueous ethanolic extract of the aerial parts of Silene gallica L. (Caryophyllaceae), growing in North-Eastern Algeria, was performed to evaluate its antioxidant activity using DPPH, hydroxyl radical scavenging and CUPRAC assays. Successive chromatographic separations of the most antioxidant n-BuOH soluble fraction yielded four acylated flavone C-glycosides, vitexin 2''-O-β-d-(4''',6'''-di-acetyl)-glucopyranoside (1), orientin-2''-O-β-d-(4''',6'''-di-acetyl)-glucopyranoside (2), orientin-2''-O-β-d-(6'''-feruloyl)-glucopyranoside (3), and orientin-2''-O-β-d-(6'''-sinapoyl)-glucopyranoside (4), as well as six known compounds including four flavonoids (5-8), a phenylpropanoid glycerolglucoside (regaloside A) (9), and a phytoecdysteroide (20-hydroxyecdysone) (10). Their structures were established by UV, 1D, ²D NMR, and HR-ESI-MS spectral data, in addition to comparison with literature data. The antioxidant activity of the crude extracts, fractions and compounds 1-8 was evaluated. Two acylated orientin glycosides (3 and 4) displayed the strongest antioxidant activity.     

Firmiana (Malvaceae: Sterculioideae) fruits from the Upper Miocene of Yunnan,Southwest China

A new species of Firmiana Marsili is recognized and described based on capsules from the Late Miocene Lincang flora of Yunnan, China. Firmiana yunnanensis nov. sp. is represented by opened, dehiscent, membranous follicles with a weak, sinuous midvein, obtuse secondary veins and thick marginal vein. The follicles conform in shape and venation with those of extant species of Firmiana, a genus now distributed in eastern Africa, Indo-Malaysia, and eastern and southeastern Asia. This fossil species occurred within the native distribution of extant Firmiana species. It provides new information on fossil history, paleoecology, as well as on the plant diversity of the Lincang flora.     

Flavonoid aglycones in the resin of Hazardia squarrosa var. Grindelioides

Thirty three flavonoid aglycones have been identified from the external stem and leaf resin of Hazardia squarrosa var. grindelioides by TLC co-chromatography with authentic samples. The occurrence of compounds with oxygenation at C-6 and C-5′, which are also found in the genus Haplopappus, supports the previously believed close relationship between these two genera.     

Growth and mitotic potential of multicelled fibers of cotton (Malvaceae)

We tested the hypothesis that the growth of multicelled cotton fibers of Gossypium hirsutum, cultivar MD51 ne, occurs exclusively within the tip cell. Direct cellular measurements proved the hypothesis incorrect. The results show that all cells within a fiber grow and that the relative growth of the tip cell is reduced as the number of cells per fiber increases. Also, measurements of two- and three-celled fibers show that the two daughter nuclei in two-celled fibers differ. The ability to divide resides primarily, if not exclusively, with the basal cell. Thus, the fate of the tip-cell nucleus is fixed while that of the base cell is not. This rule is unaltered by the presence of IAA (indoleacetic acid) and GA3 (gibberellic acid-3) in the culture medium.     

HPLC analysis of leaf surface flavonoids for the preliminary classification of birch species

Flavonoid aglycones found on the surfaces of birch (Betula spp.) leaves may constitute up to 10% of the dry weight of the leaf. A facile extraction and HPLC procedure has been developed that can be used for the preliminary classification of birch species according to the patterns of their leaf surface flavonoids. The procedure involves no complex sample preparation steps, and is able to provide HPLC chromatograms from fresh leaves in less than 30 min. If necessary, leaves do not even need to be removed from the tree. Since the genus Betula is taxonomically complex and separation of different birch species can be problematic, the developed method was applied to 15 Betula species and four sub-species of Betula pendula Seven of the studied species were classified as B. pubescens and eight as B. pendula-type birches. The remaining four species did not belong to either of these two classes on account of their unique pattern of external flavonoids. The difference between the leaf surface flavonoid composition of B. pubescens and B. pendula type birch species was unambiguously clear, and the developed method could reliably distinguish between the two species. Whilst leaf surface flavonoids can be valuable chemotaxonomic markers, they classify birch species differently from morphological markers. Birch species with diploid chromosome sets did not contain any of the flavanones that were present in the leaves of other species. The close relationship between the occurrence of some flavonoid aglycones and the ploidy level of Betula species suggests that these chemotaxonomic markers may be useful both in taxonomic and phylogenetic analyses.