Isolation of Laurus nobilis Leaf Polyphenols: A Review on Current Techniques and Future Perspectives

In recent years, the market demand for products enhanced with ingredients derived from natural products, such as polyphenols, is rapidly increasing. Laurus nobilis L., known as bay, sweet bay, bay laurel, Roman laurel or daphne is an evergreen Mediterranean shrub whose leaves have traditionally been used in cuisines and folk medicine due to their beneficial health effects, which can nowadays be scientifically explained by various biological activities of the leaf extracts. Many of these activities can be attributed to phenolic compounds present in L. nobilis leaves which include flavonoids, phenolic acids, tannins (proanthocyanidins) and lignans. In order to enable efficient industrial utilization of these valuable compounds, it is crucial to establish optimal extraction procedures resulting in the highest yields and quality of the extracts. This paper offers the first systematic review of current literature on the influence of conventional and advanced extraction techniques, including microwave-assisted, ultrasound-assisted, enzyme-assisted, supercritical-CO2 and mechanochemical-assisted extraction on the phenolic content of L. nobilis leaf extracts, allowing more efficient planning of further research and simplifying the steps towards industrial utilization of this plant.

Nutritional and Pharmacological Properties of Bay Leaves (Laurus nobilis L.)

Laurus nobilis L., commonly known as bay leaves, is native to the southern Mediterranean region. It is a small tree belonging to the genus Laurus of the family Lauraceae. The essential oils created from the different parts of this plant, such as the leaves and flowers, have been used in the food, drug, and cosmetic industries. The essential oil chiefly consists of 1,8-cineole, sabinene, α-pinene, and p-Cymene. Researchers have reported that bay leaves possess various biological and pharmacological properties, such as antibacterial, antifungal, antioxidant, insecticidal, and nematicidal activities. Pharmacological studies found that bay leaf oil could be a promising candidate with the potential for designing new drugs. The goal of this review is to summarize the ethnomedicinal importance, phytochemistry, and wide spectrum of pharmacological and therapeutic applications of bay leaves, which will be useful to researchers for further study.

Selection of the optimal extractant for the extraction of phenolic compounds from Laurus nobilis L. leaves

Aim. To select the optimal extractant for the extraction of a number of groups of phenolic compounds from Lаurus nоbilis L. leaves based on the determination of the quantitative content of these groups in the extracts obtained. Materials and methods. Lаurus nоbilis L. leaves were harvested in November 2020 from artificially cultivated specimens aged 5 – 7 years. The quantitative determination of polyphenols was performed using the spectrophotometric method at a wavelength of 760 nm in accordance with the requirements of the Supplement of the State Pharmacopoeia of Ukraine (SPhU) 1.2 (2.8.14). The quantitative content of this group of compounds was calculated with reference to pyrogalol and dried substance. The quantitative determination of the amount of hydroxycinnamic acids was performed according to the SPhU 2.2 monograph “Orthosyphon stamen (kidney tea) leavesN” by the spectrophotometric method at a wavelength of 505 nm and calculated with reference to rosmarinic acid. The quantitative determination of the amount of flavonoids was performed according to the SPhU 2.0 monograph “Hawthorn leaves and flowers” by the spectrophotometric method at a wavelength of 410 nm and calculated with reference to hyperoside.Results and discussion. The analysis of the results for the quantitative determination of polyphenols, the amount of hydroxycinnamic acids and the amount of flavonoids in extracts from Lаurus nоbilis L. leaves obtained using water, water-ethanol mixtures and 96 % ethanol showed that 70 % ethanol was optimal for extracting compounds of these groups. The quantitative content of polyphenols (calculated with reference to pyrogalol) was not less than 21 %, the amount of hydroxycinnamic acids (calculated with reference to rosmarinic acid) – not less than 3 %, the amount of flavonoids (calculated with reference to hyperoside) – not less than 5 %. Conclusions. For the first time, the quantitative content of a number of groups of phenolic compounds (polyphenols, the total amount of hydroxycinnamic acids, and the total amount of flavonoids) in Lаurus nоbilis L. leaves extracts obtained using various extractants has been determined. On this basis, the optimal extractant – 70 % ethanol for the extraction of phenolic compounds has been selected. The results obtained will be used when developing the technology for obtaining substances from Lаurus nоbilis L. leaves.

Linking Man and Nature: Relictual Forest Coenosis with Laurus nobilis L. and Celtis australis L. in Antica Lavinium, Italy

The Mediterranean basin has been a refugium for relict plant taxa and native laurophyllic forests. The Latium coasts and, especially, the Antica Lavinium site, host relict forest communities, whose natural importance is enriched by their cultural value. Here, we aim at investigating the ecological framework, cultural and historical values, and management over time, of relict communities that have Laurus nobilis and Celtis australis as their priority habitats. To achieve this, we performed vegetation surveys and we conducted statistical analyses (PCA, NMDS). Among the 45 vegetation surveys, 25 were characterized by the two target species. The PCA analysis highlighted how the L. nobilis formations and the mixed formations with C. australis present some differences but are not sufficient to describe different coenosis. The comparison among similar forests in central and southern Italy confirmed the wide coenological amplitude of L. nobilis with respect to other laurophyllic species. Antica Lavinium has an overall good preservation of laurel forest formations, but also of mixed formation with C. australis. In the area, historical, cultural, and natural characteristics mutually contributed to the development of human civilizations and plant communities, highlighting their deep linkage.

DEFNE (Laurus nobilis L.) BİTKİSİNİN FENOLOJİK DÖNEMLERİNİN BELİRLENMESİ

Bu çalışmada İzmir ili Çeşme yarımadasındaki iki farklı alan olan Urla ve Karaburun’da yetişen doğal defne popülasyonunda iki yıl süreyle fenolojik gözlemler yapılmıştır. Çalışmada erkek ve dişi ağaçlar ayrı ayrı incelenmiştir. Ağaçlarda tomurcukların uyanması, çiçeklenme ve meyve olgunlaşması ikinci yıl daha erken gerçekleşmiştir. Her iki bölgedeki ağaçların fenolojilerinde bazı farklılıklar saptanmış ve genel olarak Urla’ da vejetasyonun daha erken başladığı tespit edilmiştir. Yıllar ve bölgeler arasındaki farklılıkların sıcaklıktan kaynaklandığı ortaya konulmuştur. Anahtar kelimeler: Defne, Fenoloji, Çeşme yarımadası, İzmir, Ege bölgesi