Herbal Extracts: Preparation-Analysis-Quality Control-Biological Characterization

Herbal extracts held a significant role in therapeutics of all times and places, and thus studies have been done on total herbal extracts (botanicals) and on their isolated natural products. Today, both the European Medicines Authority (EMA) and the Food and Drug Authority have recognized the phytotherapeutic formulations (active plant extracts) as important medicinal products. The major obstacles in the study and establishment of those herbal medicinal products according to the dictates of modern pharmacology, are the difficulty to properly characterize those complex mixtures, containing phenolic acids and esters, polyphenols, terpenes, alkaloids, glucosinolates, simple or complex carbohydrates, peptides, etc, and the instability in their composition and thereof their effectiveness.

In our Laboratory, the study of herbal extracts is performed in terms of the characterization of their composition via chromatographic and spectroscopic techniques, the development of validated analytical methods for their quality control and the characterization of their biologic properties.

Natural Products

Isolation of natural products is penultimate to their analysis and characterization in biological assays. In our Laboratory we are working on the isolation and characterization of crocins from the styles of indigenous Crocus taxa and of diterpenes from Sideritis clandestina extracts.

The main projects that are still under way in our Laboratory are presented below.

• Greek Saffron-Krokos Kozanis-flower’s styles/ stigmas of different taxa of Crocus

Its styles are rich in some unusually water-soluble apocarotenoids, the crocins. We have developed validated methods for the analysis of the cultivated Crocus sativus stigmas and are also working on the characterization of the styles from indigenous Crocus taxa, i.e. C. nivalis, C. cartrightianus, C. oreocreticus. Some new crocins in C. nivalis have already been identified. Their antioxidant properties are being studied in vitro and in vivo.

• Berries and Grapes

Blueberries, strawberries and grapes are rich in anthocyanins and other polyphenols. In the past we have investigated the effect of consuming wild blueberries (Vaccinium angustifolium fruits) on the macromolecular composition of aortas, the in vitro antioxidant properties of wild blueberries extract in different cell lines and the effect on learning-memory, and we studied the phytochemical composition of blueberries leaves (Vaccinium corymbosum) cultivated in Greece with regard to the their ability to prevent the occurrence of neonatal cataracts and thereof selenium-induced cerebral and liver oxidative stress in neonatal rats. We are currently investigating various genotypes of strawberries and novel methods for isolating the bioactive polyphenols from grape waste.

• St. John’s wort and other Hypericum taxa

As part of the study of herbs with neuroprotective effect, the well-known antidepressant properties of Hypericum perforatum (St. John’s wort) prompted us to engage in the study of this genus. Firstly, we developed an analytical HPLC method for the simultaneous determination of all major components (chlorogenic acid, quercetin glycosides and naphthodianthrones) in the methanol extract, aqueous infusions and hypericum oil preparations. This method along with LC-MS monitoring revealed significant differences in the composition of other indigenous Hypericum taxa (H. empetrifolium, H. vesiculosum, etc).

• Garlic

​The volatile composition of various garlic genotypes cultivated in Greece is under investigation.