Defining the role of a caffeic acid 3-O-methyltransferase from Azadirachta indica fruits in the biosynthesis of ferulic acid through heterologous over-expression in Ocimum species and Withania somnifera

The recombinant caffeic acid 3-O-methyltransferase gene has been cloned and characterized from Neem. The gene is involved in ferulic acid biosynthesis, a key intermediate component of lignin biosynthesis. Azadirachta indica (Neem) is a highly reputed traditional medicinal plant and is phytochemically well-known for its limonoids. Besides limonoids, phenolics are also distinctively present, which add more medicinal attributes to Neem. Caffeic acid is one of such phenolic compound and it can be converted enzymatically into another bioactive phytomolecule, ferulic acid. This conversion requires transfer of a methyl group from a donor to caffeic acid under the catalytic action of an appropriate methyltransferase. In this study, caffeic acid 3-O-methyltransferase gene from Neem (NCOMT) fruits has been isolated and heterologously expressed in E. coli. The recombinant NCOMT enzyme was purified, which exhibited efficient catalytic conversion of caffeic acid into ferulic acid, a highly potential pharmaceutical compound. The purified recombinant enzyme was physico-kinetically characterized for its catalysis. The analysis of tissue-wide expression of NCOMT gene revealed interesting pattern of transcript abundance reflecting its role in the development of fruit tissues. Further, NCOMT was heterologously overexpressed in Withania somnifera and Ocimum species, to analyze its role in ferulic acid biosynthesis in planta. Thus, the study provides insight for the endogenous role of NCOMT in ferulic acid biosynthesis en route to lignin, an important structural component. To the best of our knowledge, NCOMT pertains to be the first enzyme of the secondary metabolism that has been purified and kinetically characterized from Neem. This study may also have important prospects of applications as the observation on heterologous expression of NCOMT showed its involvement in the maintenance of the in vivo pool of ferulic acid in the plants. Thus, the study involving NCOMT opens up new dimensions of metabolic engineering approaches for the biosynthesis of potential therapeutically important phytomolecules in heterologous systems.

Development of high-performance thin layer chromatography method for identification of phenolic compounds and quantification of rosmarinic acid content in some species of the Lamiaceae family

Aim:

Representatives of Nepetoideae Burnett subfamily are promising species of the Lamiaceae Martinov family because of accumulating such valuable groups of secondary metabolites as terpenoids and polyphenols. A high-performance thin layer chromatography (HPTLC) fingerprint method for the qualitative determination of phenolic compounds and for the quantification of rosmarinic acid (RA) content in methanol extracts of five species of this subfamily was developed for the first time.

Materials and Methods:

Dried aerial parts of Dracocephalum moldavica L., Ocimum americanum L., Lophanthus anisatus (Nutt.) Benth., Monarda fistulosa L., and Satureja hortensis L. collected in flowering period were macerated with methanol. The HPTLC analysis was conducted using the CAMAG analytical system (Muttenz, Switzerland). The comparative analysis of RA contents was performed by HPTLC densitometric detection at λ = 366nm.

Results:

Identification of polyphenols in the investigated herbs was performed by comparison of a color and R_f of the chromatographic zones with six reference standards: rutin, apigenin, luteolin, caffeic acid, chlorogenic acid, and RA. HPTLC method was also validated for the quantification of RA in the extracts of investigated herbs. RA contents decreased in such a sequence: D. moldavica (24.83 ± 0.78mg/g) > M. fistulosa (20.32 ± 0.64mg/g) > O. americanum (19.59 ± 0.61mg/g) > S. hortensis (18.77 ± 0.52mg/g) > L. anisatus (12.61 ± 0.43mg/g).

Conclusion:

Obtained data can facilitate the differentiation of investigated species using the chromatographic fingerprints of their phenolic compounds. Developed and validated HPTLC method provides an approach to estimate RA content as a common marker of investigated herbs.

Application of the Folin-Ciocalteu method to the evaluation of Salvia sclarea extracts

Polyphenols are valuable group of phytoconstituents due to their high antioxidant activity and healing properties. Antioxidant properties of sages are attributed mainly to a high level of phenolic compounds. The aim of the present study was to elaborate an analytical procedure for the evaluation of the content of secondary metabolites of the polyphenol nature in the herb of Clary Sage (Salvia sclarea L.). Four crude extracts of Salvia sclarea herb obtained with different technologies were used to develop an analytical procedure for the total phenolic content (TPC) assay by spectrophotometric method. The optimum conditions for the analysis (time of the reaction, wavelength, and reference substances) were chosen and experimentally justified (60–80 min, 760 nm, gallic acid and rutin, respectively). Under these conditions, the developed analytical procedure is robust in the indicated time and easy for performing in phytochemical or technological laboratories. The yield of TPC from the herb of Salvia sclarea was the highest in the extracts prepared by heating at a temperature of 36–46 °C and with using the ultrasonic bath. TPC was the highest in the extract in which solvent-to-herb ratio was the least (10:1) and particle size was in the range of 2–5 mm. As a result of the studies, the analytical procedure of the determination of TPC was developed and its parameters were justified. This methodology complies with the requirements for pharmaceutical analysis to ensure the reliability of results during pharmaceutical development and routine control of Salvia sclarea extracts.

Chemical Analysis of the Herbal Medicine Salviae miltiorrhizae Radix et Rhizoma (Danshen)

Radix Salviae miltiorrhizae et Rhizoma, known as Danshen in China, is one of the most popular traditional Chinese medicines. Recently, there has been increasing scientific attention on Danshen for its remarkable bioactivities, such as promoting blood circulation, removing blood stasis, and clearing away heat. This review summarized the advances in chemical analysis of Danshen and its preparations since 2009. Representative established methods were reviewed, including spectroscopy, thin layer chromatography, gas chromatography, liquid chromatography (LC), liquid chromatography-mass spectrometry (LC-MS), capillary electrophoresis, electrochemistry, and bioanalysis. Especially the analysis of polysaccharides in Danshen was discussed for the first time. Some proposals were also put forward to benefit quality control of Danshen.