Phytochemical Study of Juglans regia L. Pericarps from Greece with a Chemotaxonomic Approach

Abstract

Phytochemical research of different polarity extracts from green Juglans regia L. pericarps from Greece afforded 32 compounds: four pentacyclic triterpenes (1 - 4), three sesquiterpenes (5 - 7), four tetralones (8 - 11), two naphthoquinones (12 and 13), seven phenolic acids (14 - 20), one diarylheptanoid (21), one neo-lignan (22), seven flavonoids (23 - 29), two phenylethanoids (30 and 31) and one hydrolysed tannin (32). Compounds 4 and 29 are isolated for the first time from the species, while compounds 3, 7, 20, 22, 23, 24, 25, 26, 28, 30 are reported for the first time in Juglandaceae. Chemotaxonomic significance of isolated compounds into Junglandaceae family is thoroughly discussed.

A Comprehensive Review on the Chemical Constituents and Functional Uses of Walnut (Juglans spp.) Husk

“…It has been reported that juglone was the most important phenolic compound with the highest content. This naphthoquinone was also detected in other investigations [23,24,26,121,122,136]. Recently, the 3-methoxy derivative of juglone was identified for the first time in Persian walnut husks [121].…”

“…This naphthoquinone was also detected in other investigations [23,24,26,121,122,136]. Recently, the 3-methoxy derivative of juglone was identified for the first time in Persian walnut husks [121]. Meanwhile, 3-methoxy and 2-methoxy juglone have been found in the green walnut husk of J. mandshurica Maxim [144].…”

“…Green pericarps have been used in Chinese traditional medicine for their anti-cancer and antioxidant properties as well as for the treatment of pain, inflammation, and skin diseases [120]. The leaves of the different walnut species were traditionally used in several European countries to alleviate minor inflammatory skin disorders [121]. The walnut husk is an agro-industrial residue that is available after walnut farming and processing activities [122].…”

“…Ellagic acid and tannic acid are two hydrolysable tannins that are present in the walnut husk (Table 2 and Figure 2). Ellagic acid has been detected as a hydrolysable tannin in the husk of J. regia L. [23,24,26,121,122]. Tannic acid is another compound that has been identified in the husk of the Persian walnut [28].…”

“…The authors claimed that among the identified chemicals, compounds 5,8-dihydroxy-4-methoxy-α-tetralone, 4,5-dihydroxy-α-tetralone, and 5-hydroxy-4-methoxy-α-tetralone were isolated for the first time from J. regia L. green husk extract. Moreover, regiolone, along with the above-isolated compounds, is also reported as a tetralone in the husk of J. regia L. [121]. ( S )-regiolone has been identified in the husks of J. mandshurica Maxim [144].…”