Functional characterization of L-tryptophan transport across mammalian cornea

In last few years transporter targeted drug delivery has drawn attention of research to identify and explore various nutrient transport systems including amino acid transporters for better drug delivery. The aim of present research work is to investigate the transport characteristics of L-tryptophan (L-try) across goat cornea. Transport of L-try was investigated using a glass diffusion cell for effect of concentration, pH, presence of other amino acids or metabolic inhibitor or dipeptide and tripeptide. The amount of L-try transported increased as the pH of L-try aqueous solution increased from 5 to 9. Inhibition was observed in L-try transport in absence of sodium ions where L-try solution was made isotonic with dextrose. Amino acids like L-histidine, L-arginine, L-lysine (cationic), L-glutamic acid, L-aspartic acid (anionic), glycine and L-proline (neutral) inhibited the L-try transport as compared to control (L-try alone). In presence of sodium azide and Ouabain the inhibition in L-try transport across goat cornea was observed while no marked inhibition was observed on L-try transport across goat cornea in presence of aspartame and glutathione. The L-try transport was favored up to concentration 1% w/v and at higher pH in presence of sodium ions through excised goat cornea. Functional presence of a sodium dependent L-try transport system as inhibited by ouabain having affinity to cationic and neutral amino acid is evident on goat cornea.Keywords: Cornea; Amino acid; Tryptophan; Transpor

Formulation and evaluation of mastic gum as a compression coat for colonic delivery of 5-flurouracil

Mastic gum has been reported to possess considerable anti-tumor activity against human colorectal cancer. The purpose of this work was to evaluate mastic gum in formulation of colon-specific 5-flurouracil delivery system for effective treatment of colorectal cancer. Compression coated tablets, containing 5-flurouracil in the core tablet coated with 200 mg of different coating materials containing various proportions of mastic gum were evaluated for their 5-flurouracil in vitro release. The results indicated that the concentrations of mastic gum, sodium chloride as well as hydroxypropyl methyl cellulose (HPMC) in the coating materials significantly modify the drug release. The coating material (F6) consisted of 60% mastic gum, 15% sodium chloride and 25% HPMC is considered as a promising formula for achieving colon targeting of 5-flurouracil. Further, gamma-scintigraphic studies were carried out in healthy male volunteers to evaluate in vivo release of F6. The results showed that tablets remained intact in stomach and small intestine, however partial and complete release of the tracer occurred in the colon. The in-vitro antitumor activity of 5-flurouracil-mastic gum combination mixed in a ratio representing their concentrations in tablets coated with F6 was carried out against colon cancer cell line using MTT assay. The results revealed that 5-flurouracil-mastic gum mixture was more effective in arresting cell growth in comparison to that shown by 5-flurouracil or mastic alone. In conclusion, this new colonic drug delivery system is potentially useful for 5-flurouracil colon targeting. However, clinical benefits of using mastic in formulation of 5-flurouracil colonic tablets need further evaluation