Preparation and Properties of Polyallenes. II. Phase Transitions of Polyallene

Polyallenes prepared with the aid of organoaluminum-VOCl₃ catalysts appear to exist in three distinct phases: two crystalline phases (I and II) and an amorphous phase. Phase I shows two strong X-ray diffraction peaks at d = 5.62 Å and d = 4.04 Å; phase II has three strong peaks at d = 6.28 Å, d = 5.03 Å, and d = 4.21 Å. The band of the amorphous phase has its maximum at about d = 5.6 Å.     

Development of Pesticides Based on Phytoalexins.: Part 1: Design and Synthesis of Flavanone Analogues via Bioisosterism Substitution

In order to search for novel fungicides with high activity, a series of 2‐heteroaryl‐4‐chromanones were designed and synthesized via bioisosterism substitution. The structures of all new compounds were confirmed by spectroscopic methods and microanalyses. Preliminary bioassays indicated that some compounds showed fungicidal activity against Rhizoctonia solani, Fusarium oxysporum, Physalospora piricola and Cercospora beticola.     

Bioguided Isolation and Antiproliferative Activity of Constituents from Smilax korthalsii A.D.C. Leaves

Ethyl acetate extract of Smilax korthalsii A.D.C. leaves exhibited antiproliferative activity on leukaemia carcinoma K562, hepatic liver cancer cells WRL and colorectal carcinoma with IC₅₀ of 125.20, 46.10 and 160.00 μM respectively. Isolation of the bioactive ethyl acetate extract of Smilax korthalsii A.D.C. leaves gave eight compounds; 3β‐hydroxyspirost‐5‐ene (diosgenin), 1 , β‐sitosterol, 2 , lup‐5,11,20‐trien‐23‐ol, 3 , uneicos‐9‐enoic acid, 4 , ethylheptadecan‐17‐oic‐9‐enoate, 5 , cis‐octadec‐9‐enoic acid, 6 , hexadec9‐enoic acid, 7 and 11‐methyltridec‐12‐en‐1‐ol, 8 . The isolated compounds were tested against four human cancer cell lines: leukaemia carcinoma, K‐562; hepatic liver cancer cells, WRL; colorectal carcinoma, COLO; and breast carcinoma, MCF‐7 using the MTT assay. Diosgenin 1 exhibited significant antiproliferative activity against all four cell lines (IC₅₀; K562=6.25, WRL=14.34, COLO=38.00, MCF‐7=12.40 μM), while compounds 3, 6 and 7 inhibited the growth of K‐562 at 20, 50 and 100 μM concentrations with IC₅₀ of 90.20, 75.92 and 50.72 μM respectively. Other isolated compounds also showed cytotoxic properties against K‐562, WRL and COLO, but showed low inhibition of MCF‐7.