Phytochemical Investigation by Microwave‐Assisted Extraction of Essential Oil of the Leaves of Walnut Cultivated in Algeria

Abstract

Walnut (Juglans regia L.) leaves are used traditionally as an herbal tea indicated for non-insulindependent diabetics. In recent years, the type-II diabetes is occurring worldwide with increasing frequency. Thus, there is an urgent need to explore the new beneficial biomolecules on the human health. Our objective was to investigate, for the first time, the volatiles profile of Juglans regia L. leaves from Algiers region. The extraction of essential oil of fresh plant material was performed by microwaveassisted hydrodistillation (MAHD), for the first time, a relatively recent method, then by the conventional hydrodistillation technique (HD) for comparison. The collected extracts were analyzed by GC-FID and GC/MS using two capillary columns with different polarity. Extraction time of 1 h by MAHD provided higher yields (0.050 AE 0.001% (w/w)) than by HD (0.030 AE 0.006% (w/w)) after 3 h. A total of 38 compounds were identified using both techniques. Essential oils had similar qualitative but different quantitative composition in terms of chemical compounds. The MAHD method improved yield while reducing the extraction time. The sesquiterpenes were the dominant family in both MAHD and HD essential oils with b-caryophyllene being the major constituent. Monoterpenes, including hydrocarbon and oxygenated, prevail in HD volatile fraction with b-pinene and eucalyptol, respectively, as major components.

A Comparative Review on the Extraction, Antioxidant Content and Antioxidant Potential of Different Parts of Walnut (Juglans regia L.) Fruit and Tree

“…Juglone is the natural phenolic compound in walnut, which is found in fresh walnut leaves [113,114]. The leaves of J. regia L. are considered as a good source of flavonoids [115] and other beneficial compounds [116,117].…”

11-Hydroxy-2,4-cycloeudesmane from the Leaf Oil of Juglans regia and Evaluation of its Larvicidal Activity

“…Previous studies resulted in the isolation of phenolics [9] and volatile constituents [8,10]. The leaf volatiles of J. regia from different localities are summarized in Table 1 [11][12][13][14][15][16][17]. In the present study, the leaf essential oils (EOs) of J. regia obtained from two different locations were investigated by GC-FID and GC/MS, and a new cycloeudesmane-type sesquiterpene (1) was isolated.…”

Superior Valorisation of Juglans regia L. Leaves of Different Maturity through the Isolation of Bioactive Compounds

“…Juglone is the main natural phenolic compound identified in walnut [24,25], being found in fresh walnut leaves [26]. Moreover, the leaves of Juglans regia L. are considered a good source of flavonoids [27] and other important bioactive compounds [28,29]. Thus, several studies reported the presence of different valuable compounds in the walnut leaves, such as quercetin 3-oglucoside and quercetin pentosides, gallic acid, 3-caffeoylquinic acid, 3-ρ-coumaroylquinic acid, protocatechuic acid, 4-caffeoylquinic acid, 4-ρ-coumaroylquinic acid, ρ-coumaric acid quercetin-3-o-deoxyhexoside, and other important phenolic derivatives [30][31][32].…”