Polymorphic species

What form of the solid is present (i.e., particle morphology, polymorphic species, degree of crystallinity, (an)hydrate), and is this form thermodynamically stable over the temperature and relative humidity range that the solid is expected to encounter ... 

Taxonomically, the genus Ipomoea is extremely difficult. The binomial Ipomoea tricolor has already crept into the limited literature that has groyrn up in connection with this second kind, of ololiuqui. Inasmuch as some confusion may result in the use of two names— ipomoea tricolor and I. violacea- we should point out that, after a study ofplant material and the taxonomic history of these binomials, I am in agreement with the American specialist in the Convolvulaceae, H. D. House (House, H. D. The North American species of the genus Ipomoea in Ann. N.Y. Acad. Sci. 18 C19083 259), that both names actually refer to one polymorphic species. In this case, then, the older name is Ipomoea Violacea L. Sp. Pl. (1753) 161, which should be used in preference to its synonym I. tricolor Cav. Ic. Pl. Par. 3 (1794) 5, t. 208. 

Variations neither useful nor injurious would not be affected by natural selection, and would be left either a fluctuating element, as perhaps we see in certain polymorphic species, or would ultimately become fixed, owing to the nature of the organism and the nature of the conditions. ... 

Subsequently, workers in pharmaceutically related fields realized that the solid-state property differences derived from the existence of alternate crystal forms could translate into measurable differences in properties of pharmaceutical importance. For instance, it was found that various polymorphs could exhibit different solubilities and dissolution rates, and these differences sometimes led to the existence of nonequivalent bioavailabilities for the different forms. Since then, it has become recognized that an evaluation of the possible polymorphism available to a drug substance must be thoroughly investigated early during the stages of development. In various compilations, it has been reported that polymorphic species are known for most drug substances and that one should be surprised to encounter a compound for which only one structural type can be formed. 

Additional remark Also the essential oil of wild thyme, T. serpyllum [284-023-3 84776-98-7], again a polymorphous species bearing several chemotypes, is of commercial interest. A carvacrol-rich oil type may contain for example carvacrol (20-40%), thymol (1-5%), p-cymene (10-20%), y-terpinene (5-15%), bomeol, bomyl acetate, 1,8-cineol, citral, geraniol, linalool and others [284[. 

As has been noted for DTA analysis, differential scanning calorimetry can also be used to establish the melting points of polymorphic species. For example, gepirone hydrochloride has been obtained in three polymorphic forms, which were found to melt at 180°C, 200°C, and 212°C [92]. In this work, it was shown that Forms I and II, and Forms I and III, were enantiotropic pair systems, but that Forms II and III were monotropic with respect to each other. The two polymorphs of phenylephrine oxazolidine each exhibited well-defined melting... 

Lagarias, J.C., D. Goff, F.K. Klein, and H. Rapoport Cyclopeptide Alkaloids. Phencyclopeptines from the Polymorphic Species Ceanothus integerrimus. J. Nat. Prod., 42, 220 (1979). 

Probably the best known alkaloid of this group is cocaine (16), derived from the coca plant Erythroxylum coca, Eryth-roxylaceae) (White, 1989). This polymorphic species is a native of the Andes of northwestern South America. The leaves of the plant, which contain 0.5-2% cocaine, are chewed by many Andean Indians who are said to derive a feeling of well-being and alleviation of hunger pangs thereby. There is no concomitant hallucinogenic effect. Most commercially cultivated coca for the pharmaceutical industry comes from Peru and Bolivia (Boucher, 1991 Tyler et al., 1981 White, 1989). 

Breeding of the polymorph species A. absinthium in the Conthey Research Centre (Switzerland) resulted in a uniform variety accumulating c -epoxyocymene as main compound. After screening of more than 800 plants from 24 accessions originating from six countries, the researcher selected and stabilized the desired chemovariety (Simonnet et al., 2012). 

Interestingly, compound 13 is a polymorphous species of a previously synthesized, green colored, ID CP Cn(pz)2, obtained throngh a completely different procedure, where the coordination geometry of copper(It) is tetrahedral. See Elheit, M. K. Rettig, S. J. Storr,... 

Once these techniques indicate that there may be multiple polymorphs or solvates present, more complex and involved techniques such as X-ray powder diffraction or solid-state NMR (SSNMR) can be employed to confirm the initial test and provide more information about the exact polymorphic species in the API. ... 

DCPA inhibits the growth of grass species by dismpting the mitotic sequence, probably at entry (190). DCPA influences spindle formation and function (181) and causes root-tip swelling (182) and britde shoot tissue (191). It has been reported that DCPA, like colchicine and vinblastine, attests mitosis at prometaphase and is associated with formation of polymorphic nuclei after mitotic arrest (192). Pronamide also inhibits root growth by dismpting the mitotic sequence in a manner similar to the effect of colchicine and the dinitroanilines (193,194). Cinmethylin and bensuhde prevent mitotic entry by unknown mechanisms (194). 

During precipitate ageing, a gradual transformation of an initially precipitated metastable phase into a final crystalline form often occurs. The metastable phase may be an amorphous precipitate, a polymorph of the final material, a hydrated species or some system-contaminated substance (Mullin, 2001). In 1896, Ostwald promulgated his rule of stages which states that an unstable... 

The ring adopts the chair Ibrm and its dimensions are compared with those of other polymorphs in Table 15.5. Note that cyc/o-S has the smallest bond angle and dihedial angle of all poly-sulfur species for which data are available and this, Uigether with the small hole at the centre of the molecule and the efficient packing within the crystal, lead to the highest density of any known polymorph of sulfur (Table 15.6). 

Canigueral, S., R. Vila, G. Vicario, X. Tomas and T. Adzet. 1994. Chemometrics and essential oil analysis chemical polymorphism in two Thymus species. Biochem. Syst. Ecol. 22 307-315. 

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