Phytochemical Studies of Artemisia Annua L.

Artemisia annua L. belongs to the tribe Anthemideae of the Compositae and comprises some 400 species which are widely- distributed, especially in Asia, North America and Europe. A number of species are of medicinal value in traditional medicine and in particular annua has been used in China for centuries for the treatment of liver disease and malaria. In the search for effective novel antimalarial drugs, the sesquiterpene lactone, artemisinin (qinghaosu, QHS) has been isolated previously from A annua. Artemisinin is active against chloroquine-resistant Plasmodium falciparum in the treatment of cerebral malarial. It has been reported that the in vitro antimalarial activity of artemisinin and some of its derivatives is markedly enhanced by the presence of methoxylated flavones such as artemetin and casticin. Hence it was of interest to isolate other methoxylated flavones from A. annua to ascertain the extent to which such compounds may affect the activity of artemisinin. Thirty four flavonoids, including six novel flavonoids, four coumarins and two novel chromene compounds have been isolated and identified during the present investigation. Their structure elucidation is based on spectroscopic analyses (UV, 'H NMR and MS). The following compounds were identified and apart from casticin and scopoletin they have not been reported previously as constituents of A. annua : casticin, chrysoplenetin, chrysosplenol-D, circilineol, penduletin, eupatorin, axillarin, cirsiliol, tamarixetin, rhamnetin. quercetin-3-methylether, cirsimaritin, rhamnocitrin, chrysoeriol, apigenin, luteolin, kaempferol, quercetin, isorhamnetin,luteolin-4' methylether, isokaempferide, quercetagetin-3-methylether, tomentin, astragalin, luteolin-7- glucoside, quercetin-3'-glucoside, isoquercitrin, quercimeritrin,scoparonej fraxetin-8 methylether, and 5,6- dimethoxycoumarin. The following six novel flavonoids and two novel chromenes were also isolated and characterised: quercetagetin-4'-methylether, quercetagetin 3,4'-dimethylether, 5,2',4'-trihydroxy-6,7,5'-trimethoxyflavone, 5,7,8,3'-tetra hydroxy-3,4' dimethoxyflavone, quercetagetin-3-methylether-4'- glucoside, gossypetin-3-methylether-3' glucoside, 2,2,6-tri hydroxychromene and 2,2-dihydroxy-6-methoxychromene. Some of them, e.g., casticin, chrysoplenetin, chrysosplenol-D and circilineol have weak antimalarial activity and can potentiate the in vitro activity of artemisinin against Plasmodium falciparum

On 4n4n-dimensional neither pointed nor semisimple Hopf algebras and the associated weak Hopf algebras

For a class of neither pointed nor semisimple Hopf algebras $H_{4n}$ of dimension $4n$, it is shown that they are quasi-triangular, which universal $R$-matrices are described. The corresponding weak Hopf algebras $\mathfrak{w}H_{4n}$ and their representations are constructed. Finally, their duality and their Green rings are established by generators and relations explicitly. It turns out that the Green rings of the associated weak Hopf algebras are not commutative even if the Green rings of $H_{4n}$ are commutative.Comment: 18 page

Projective class rings of a kind of category of Yetter-Drinfeld modules

In this paper, all simple Yetter-Drinfeld modules and indecomposable projective Yetter-Drinfeld modules over a family of non-pointed 8m-dimension Hopf algebras of tame type with rank two, are construted and classified. The technique is Radford's method of constructing Yetter-Drinfeld modules over a Hopf algebra. Furthermore, the projective class rings of the category of Yetter-Drinfeld modules over this class of Hopf algebras are described explicitly by generators and relations

BGP-Reflection Functors and Lusztig's Symmetries: A Ringel–Hall Algebra Approach to Quantum Groups

AbstractAccording to the canonical isomorphisms between the Ringel–Hall algebras (composition algebras) and the quantum groups, we deduce Lusztig's symmetries T″i,1,i∈I, by applying the Bernstein–Gelfand–Ponomarev reflection functors to the Drinfeld doubles of Ringel–Hall algebras. The fundamental properties of T″i,1 including the following can be obtained conceptually. (1) T″i,1,i∈I induce automorphisms of the quantum groups Uq(g) and on the integrable modules. (2) T″i,1,i∈I satisfy the braid group relations. This extends and completes the results of B. Sevenhant and M. Van den Bergh (1999, J. Algebra221, 135–160)

Projective class rings of the category of Yetter-Drinfeld modules over the 2-rank Taft algebra

In this paper, all simple Yetter-Drinfeld modules and indecomposable projective Yetter-Drinfeld modules over the $2$-rank Taft algebra $\mathcal{\bar{A}}$ are construted and classified by Radford's method of constructing Yetter-Drinfeld modules over a Hopf algebra. Furthermore, the projective class ring of the category of Yetter-Drinfeld modules over $\mathcal{\bar{A}}$ is described explicitly by generators and relations

On finite-dimensional irreducible modules for the universal Askey-Wilson algebra

Let $\Delta_q$ be the universal Askey-Wilson algebra. If $q$ is not a root of unity, it is shown in the Huang's earlier paper that an $(n+1)$-dimensional irreducible $\Delta_q$-module is a quotient $V_n(a, b, c)$ of a $\Delta_q$-Verma module with ${\textbf{ Condition A: }} \; abc, a^{-1}bc, ab^{-1}c, abc^{-1} \notin \left \{q^{n-2i+1}| 1 \leq i \leq n\right \}.$ The aim of this paper is to discuss the structures of $(n+1)$-dimensional $\Delta_q$-modules $V_n(a, b, c)$ when the given triples $(a, b, c)$ do not satisfy Condition A