Profile of biological characterizations and clinical application of corneal stem/progenitor cells.

Corneal stem/progenitor cells are typical adult stem/progenitor cells. The human cornea covers the front of the eyeball, which protects the eye from the outside environment while allowing vision. The location and function demand the cornea to maintain its transparency and to continuously renew its epithelial surface by replacing injured or aged cells through a rapid turnover process in which corneal stem/progenitor cells play an important role. Corneal stem/progenitor cells include mainly corneal epithelial stem cells, corneal endothelial cell progenitors and corneal stromal stem cells. Since the discovery of corneal epithelial stem cells (also known as limbal stem cells) in 1971, an increasing number of markers for corneal stem/progenitor cells have been proposed, but there is no consensus regarding the definitive markers for them. Therefore, the identification, isolation and cultivation of these cells remain challenging without a unified approach. In this review, we systematically introduce the profile of biological characterizations, such as anatomy, characteristics, isolation, cultivation and molecular markers, and clinical applications of the three categories of corneal stem/progenitor cells.

Effects of brewing water on the sensory attributes and physicochemical properties of tea infusions.

The effects of brewing water on the sensory attributes and physicochemical properties of tea infusions made from Chinese teas were investigated. The tea infusions brewed in water with higher pH and total dissolved solids (TDS), generally had a darker color and lower overall sensory acceptability. Moreover, those infusions had less catechins, particularly galloylated-catechins, and lower antioxidant capacity. The teas with less fermentation contained more galloylated-catechins and had higher antioxidant capacity, but were much more susceptible to high mineral brewing water. Green tea was proved to be the most susceptible one, whereas dark tea the most stable one. Green tea infusions prepared with higher pH/TDS water were more rapidly oxidized, resulting in a darker color due to polymerization of catechins, when exposed to the air. These findings suggested that low mineral brewing water was better for Chinese tea, both from the sensory and health benefit perspectives.

Diastereoselective total synthesis of (±)-schindilactone†A, Part†1: Construction of the ABC and FGH ring systems and initial attempts to construct the CDEF ring system.

First-generation synthetic strategies for the diastereoselective total synthesis of schindilactone A (1) are presented and methods for the synthesis of the ABC, FGH, and CDEF moieties are explored. We have established a method for the synthesis of the ABC moiety, which included both a Diels-Alder reaction and a ring-closing metathesis as the key steps. We have also developed a method for the synthesis of the FGH moiety, which involved the use of a Pauson-Khand reaction and a carbonylative annulation reaction as the key steps. Furthermore, we have achieved the construction of the central 7-8 bicyclic ring system by using a [3,3]-rearrangement as the key step. However, unfortunately, when this rearrangement reaction was applied to the construction of the more advanced CDEF moiety, the anticipated annulation reaction did not occur and the development of an alternative synthetic strategy would be required for the construction of this central core.

Diastereoselective total synthesis of (±)-schindilactone†A, Part†2: Construction of the fully functionalized CDEFGH ring system.

The successful synthesis of the highly complex model compound (2) of the CEFGH ring system of schindilactone A (1) is described. Several synthetic methodologies were developed and applied to achieve this goal, including ring-closing metathesis (RCM) and Co-thiourea-catalyzed Pauson-Khand reactions. Furthermore, two independent approaches were developed for the construction of the GH ring of model compound 2, the key steps of which included Pd-thiourea-catalyzed carbonylative annulation, methylation, and sequential RCM/oxa-Michael-addition reactions. The chemistry developed herein has provided a greater understanding of the synthesis of schindilactone A (1) and its analogous compounds of the same family.

Diastereoselective total synthesis of (±)-schindilactone†a, Part†3: The final phase and completion.

The final phase for the total synthesis of (±)-schindilactone A (1) is described herein. Two independent synthetic approaches were developed that featured Pd-thiourea-catalyzed cascade carbonylative annulation reactions to construct intermediate 3 and a RCM reaction to make intermediate 4. Other important steps that enabled the completion of the synthesis included: 1) A Ag-mediated ring-expansion reaction to form vinyl bromide 17 from dibromocyclopropane 30; 2) a Pd-catalyzed coupling reaction of vinyl bromide 17 with a copper enolate to synthesize ketoester 16; 3) a RCM reaction to generate oxabicyclononenol 10 from diene 11; 4) a cyclopentenone fragment in substrate 8 was constructed through a Co-thiourea-catalyzed Pauson-Khand reaction (PKR); 5) a Dieckmann-type condensation to successfully form the A ring of schindilactone A (1). The chemistry developed for the total synthesis of schindilactone A (1) will shed light on the synthesis of other family members of schindilactone A.