Chemical Studies on Crude Drug Processing. IX. On the Constituents of Rehmanniae Radix. (3). Absolute Stereostructures of Rehmaionosides A, B, and C, and Rehmapicroside, Biologically Active Ionone Glucosides and a Monoterpene Glucoside Isolated from Chinese Rehmanniae Radix.

The article provides brief information about cardiotonic, sedative, cytostatic, diuretic, and antibacterial effects of biologically active compounds of Adonis L. (Ranunculaceae) species. Chemical studies allowed to identify the cardiac glycosides, or cardenolides: or cardenolides: adontoxin, adonitol, adonitoxigenin, acetyldigitoxin and others. In scientific medicine, it is currently allowed to use Adonis vernalis L. Other types of Adonis have a similar chemical composition and are offered as substitutes for this official species, for example, Adonis apennina L. Many Adonis species have limited natural resources, and in some regions are rare, requiring conservation of their natural populations. The search for alternative sources of medicinal plant raw materials, based on this, is relevant. The experimental part of our research was carried out using the morphological and geographical method with the involvement of information on ecology and phenology. For the first time summarizes the diagnostic features of Adonis flora of Russian flora. Previously unknown structural features (shape and size of anthers) were identified that characterize the subgenera Adonanthe and Adonis. Taxonomic study of the genus Adonis of the Russian flora allowed us to determine its species composition, clarify its systematic affiliation, and nomenclature synonyms. 9 species were identified. Of these, 6 are perennials belonging to the subgenus Adonanthe, section Consiligo, which includes 2 subsections: Amurenses (2 species) and Vernales, which is differentiated into 2 rows: Apenninae (2 species) and Vernales (2 species). Subgenus Adonis is represented by 2 sections: Adonis (1 species) and Lophocarpa with sections Aestivales (1 species) and Dentatae (1 species). For all the considered species and varieties, the main distribution areas are given. A key has been compiled to determine the wild Adonis species distributed in Russia.

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Quantum-Chemical Search for Keto Tautomers of Azulenols in Vacuo and Aqueous Solution

Symmetry ◽

10.3390/sym13030497 ◽

2021 ◽

Vol 13 (3) ◽

pp. 497

Author(s):

Ewa D. Raczyńska

Keyword(s):

Aqueous Solution ◽

Quantum Chemical ◽

Biologically Active ◽

Deprotonation Reaction ◽

Chemical Studies ◽

Quantum Chemical Studies ◽

Scanty Information ◽

Derivatives Of ◽

Common Anion ◽

Tautomeric Mixture

Keto-enol prototropic conversions for carbonyl compounds and phenols have been extensively studied, and many interesting review articles and even books appeared in the last 50 years. Quite a different situation takes place for derivatives of biologically active azulene, for which only scanty information on this phenomenon can be found in the literature. In this work, quantum-chemical studies have been undertaken for symmetrically and unsymmetrically substituted azulenols (constitutional isomers of naphthols). Stabilities of two enol (OH) rotamers and all possible keto (CH) tautomers have been analyzed in the gas phase {DFT(B3LYP)/6-311+G(d,p)} and also in aqueous solution {PCM(water)//DFT(B3LYP)/6-311+G(d,p)}. Contrary to naphthols, for which the keto forms can be neglected, at least one keto isomer (C1H, C2H, and/or C3H) contributes significantly to the tautomeric mixture of each azulenol to a higher degree in vacuo (non-polar environment) than in water (polar amphoteric solvent). The highest amounts of the CH forms have been found for 2- and 5-hydroxyazulenes, and the smallest ones for 1- and 6-hydroxy derivatives. The keto tautomer(s), together with the enol rotamers, can also participate in deprotonation reaction leading to a common anion and influence its acid-base properties. The strongest acidity in vacuo exhibits 6-hydroxyazulene, and the weakest one displays 1-hydroxyazulene, but all azulenols are stronger acids than phenol and naphthols. Bond length alternation in all DFT-optimized structures has been measured using the harmonic oscillator model of electron delocalization (HOMED) index. Generally, the HOMED values decrease for the keto tautomers, particularly for the ring containing the labile proton. Even for the keto tautomers possessing energetic parameters close to those of the enol isomers, the HOMED indices are low. However, some kind of parallelism exists for the keto forms between their relative energies and HOMEDs estimated for the entire molecules.

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