Varietal Differences in Juice, Pomace and Root Biochemical Characteristics of Four Rhubarb (Rheum rhabarbarum L.) Cultivars

The complex evaluation of varietal biochemical differences in rhubarb juice, pomace and roots is highly useful to develop an efficient processing technology. Research was carried out to compare four rhubarb cultivars (Malakhit, Krupnochereshkovy, Upryamets and Zaryanka) in terms of the quality and antioxidant parameters of juice, pomace and roots. The laboratory analyses showed a high juice yield (75-82%) with a relatively high content of ascorbic acid (125-164 mg L^-1) and other organic acids (16-21 g L^-1). Citric, oxalic and succinic acids accounted for 98% of the total acids amount. The juice of the cultivar Upryamets demonstrated high levels of the natural preservatives sorbic (36.2 mg L^-1) and benzoic acids (11.7 mg L^-1), which are highly valuable in juice production. The juice pomace proved to be an excellent source of pectin and dietary fiber, whose concentrations reached 21-24% and 59-64%, respectively. The total antioxidant activity decreased according to the following sequence: root pulp (161-232 mg GAE g^-1 d.w.) > root peel (115-170 mg GAE g^-1 d.w.) > juice pomace (28.3-34.4 mg GAE g^-1 d.w.) > juice (4.4-7.6 mg GAE g^-1 f.w.), suggesting that root pulp is a highly valuable antioxidant source. The results of this research highlight the interesting prospects of the complex rhubarb plant processing for the production of juice, containing a wide spectrum of organic acids and natural stabilizers (sorbic and benzoic acids), dietary fiber and pectin (juice pomace) and natural antioxidants (roots).

Micropropagation, Genetic Fidelity and Phenolic Compound Production of Rheum rhabarbarum L

An efficient micropropagation protocol for Rheum rhabarbarum L. was developed in this study. The in vitro rhubarb plants obtained in the multiplication stage (proliferation rate: 5.0 ± 0.5) were rooted in vitro (96% rooting percentage) and acclimatized ex vitro in floating perlite, with 90% acclimatization percentage. To assess the genetic fidelity between the mother plant and in vitro propagated plants, sequence-related amplified polymorphism (SRAP) markers were used. All banding profiles from the micropropagated plants were monomorphic and similar to those of the mother plant indicating 100% similarity. Regarding the polyphenolic profile, gallic, protocatechuic, p-hydroxybenzoic, vanillic, chlorogenic, caffeic, syringic, p-coumaric and ferulic acid were present in different amounts (2.3-2690.3 μg g^-1 dry plant), according to the extracted matrix. Aglicons and glycosides of different classes of flavonoids were also identified. The rhizome extracts (both from in vitro and field grown plants) contained resveratrol, a stilbene compound with high antioxidant properties, ranging between 229.4 to 371.7 μg g^-1 plant. Our results suggest that in vitro propagation of Rheum rhabarbarum L. represents a reliable alternative to obtain a large number of true-to-type planting material with high bioactive compound content of this valuable nutritional and medicinal species.

Detection progress of selected drugs in TLC

This entry describes applications of known indicators and dyes as new visualizing reagents and various visualizing systems as well as photocatalytic reactions and bioautography method for the detection of bioactive compounds including drugs and compounds isolated from herbal extracts. Broadening index, detection index, characteristics of densitometric band, modified contrast index, limit of detection, densitometric visualizing index, and linearity range of detected compounds were used for the evaluation of visualizing effects of applied visualizing reagents. It was shown that visualizing effect depends on the chemical structure of the visualizing reagent, the structure of the substance detected, and the chromatographic adsorbent applied. The usefulness of densitometry to direct detection of some drugs was also shown. Quoted papers indicate the detection progress of selected drugs investigated by thin-layer chromatography (TLC).

Antimicrobial activity and total content of polyphenols of Rheum L. species growing in Poland

In the crude ethanol extracts obtained from the rhizome and roots of Rheum palmatum L., Rheum undulatum L. and Rheum rhaponticum L. growing in Poland concentration of polyphenols ranged from 46.11 to 76.45 mg/g. Concentration of tannins ranged from 7.07% to 8.67%, while anthracene derivatives and anthraquinones varied by species - R. palmatum measured 36.3 and 34 mg/g, while R. undulatum or R. rhaponticum did not exceed 20.4 and 18.1 or 19.8 mg/g and 16.6 mg/g, respectively. Using a broth microdilution method it was found that all of the Rheum spp. extracts were more active against reference strains of Gram-positive bacteria (Staphylococcus spp.) than against those of Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis). The strongest inhibitory effect against Staphylococcus spp. was exerted by R. undulatum extract with MIC = 125–250 μg/mL. The moderate in vitro antibacterial activity of R. undulatum suggests that this plant, often used in the European cuisine to improve flavour, may be also important and useful as an alternative or auxiliary medicine remedy in the treatment of uncomplicated superficial infections caused especially by clinically important staphylococci, potentially pathogenic S. aureus or opportunistic S. epidermidis.