Similarity analyses of chromatographic herbal fingerprints: A review

Herbal medicines are becoming again more popular in the developed countries because being “natural” and people thus often assume that they are inherently safe. Herbs have also been used worldwide for many centuries in the traditional medicines. The concern of their safety and efficacy has grown since increasing western interest. Herbal materials and their extracts are very complex, often including hundreds of compounds. A thorough understanding of their chemical composition is essential for conducting a safety risk assessment. However, herbal material can show considerable variability. The chemical constituents and their amounts in a herb can be different, due to growing conditions, such as climate and soil, the drying process, the harvest season, etc. Among the analytical methods, chromatographic fingerprinting has been recommended as a potential and reliable methodology for the identification and quality control of herbal medicines. Identification is needed to avoid fraud and adulteration. Currently, analyzing chromatographic herbal fingerprint data sets has become one of the most applied tools in quality assessment of herbal materials. Mostly, the entire chromatographic profiles are used to identify or to evaluate the quality of the herbs investigated. Occasionally only a limited number of compounds are considered. One approach to the safety risk assessment is to determine whether the herbal material is substantially equivalent to that which is either readily consumed in the diet, has a history of application or has earlier been commercialized i.e. to what is considered as reference material. In order to help determining substantial equivalence using fingerprint approaches, a quantitative measurement of similarity is required. In this paper, different (dis)similarity approaches, such as (dis)similarity metrics or exploratory analysis approaches applied on herbal medicinal fingerprints, are discussed and illustrated with several case studies.     

Stereospecific synthesis of leukotriene B4 (LTB4)

A stereospecific and chirally economical synthesis of LTB₄ starting from 2-deoxy-D-ribose is reported as part of a comprehensive and efficient approach to the Leukotrienes (A, B, C, D, E). The process includes a novel approach to chiral dienic synthons.     

Synthesis and optical properties of multibranched and C3 symmetrical oligomers with benzene or triphenylamine core and diazines as peripheral groups

We report therein the synthesis and photophysical properties of a new series of two- and tribranched compounds built up from benzene or triphenylamine as central core and electron-withdrawing diazine rings as peripheral group. The arms allowing connection between these two parts are constituted by an ethynylene linker. All these compounds are fluorescent and are of particular interest with generally good quantum yields and good Stokes shifts. Some of them have been tested for two-photon absorption (TPA) properties and had revealed interesting performances.     

Stability of Two Soliton Collision for Nonintegrable gKdV Equations

We continue our study of the collision of two solitons for the subcritical generalized KdV equations