Chemotaxonomic Significance of Flavonoids in Some Species of <em>Galium</em> (Rubiaceae) from Libya

Research Article

Austin J Plant Biol. 2016; 2(1): 1014.

Chemotaxonomic Significance of Flavonoids in Some Species of Galium (Rubiaceae) from Libya

Moubasher H¹*, Abd E¹-Ghani M¹, Al-Wakeel S¹ and Bahoor A¹

¹Department of Botany and Microbiology, Cairo University, Egypt

²Faculty of Science, Al-Marqeb University, Libya

*Corresponding author: Moubasher H, Department of Botany and Microbiology, Faculty of Science, Cairo University, Giza 12613, Egypt

Received: July 22, 2016; Accepted: September 06, 2016; Published: September 12, 2016


The flavonoid profiles of five Libyan Galium L. (Rubiaceae) species collected from different localities and habitats were investigated. Fourteen flavonoid compounds were isolated and identified using the direct comparison of chromatographic and UV spectral analyses with standard samples. The flavone compounds were identified as apigenin (1) and its 7-glycoside (2); luteolin 7-diglycoside (3), diosmetin (4) and its 7-monoglycoside (5), as well as its 7-diglycoside (6). In addition, the detected flavonol compounds were kaempferol 3-glycoside (7), 3-diglycoside (8) and 3,7-diglycoside (9); quercetin (10) and its 3-glycoside (11), 3-rutinoside (12), 3,7-diglycoside (13), and 3-diglycoside- 7-glycoside (14). The chemotaxonomic relationships of the studied species of Galium and their significance were also discussed.

Keywords: Chemosystematics; Galium; Rubiaceae; Flavonoid glycosides; biochemistry; Multivariate analysis


Galium L. is one of the largest genera of Rubieae (Rubiaceae) with more than 400 species included into 16 sections containing annual and perennial herb that are distributed in temperate and tropical regions of the world [1,2]. Certain species of Galium are found even in the Arctic zone or high elevations on tropical mountain ranges. Galium itself is problematic taxonomically, because taxa from different sections exhibit similar habit, many species are widely distributed and polymorphic, and species groups often are poorly differentiated both morphologically and geographically [3].

The flavonoid chemistry of Galium have been studied, and reported to contain predominantly flavones and flavonol aglycones and their glycosides. Earlier study by [4] isolated rutin and a mixture of flavonoids and diosmetin from Galium palustre L. Also, the glycosides of quercetin, luteolin, apigenin and kaempferol were isolated from Galium aparine [5,6]. Reported that Galium has long been known to contain substantial amounts of anthraquinones, with the roots being especially rich sources of these secondary metabolites. Bedstraw species, including G. mollugo, contain mollugin [7], flavonoids [8], coumarins, phenolic acids, and iridoid glucosides [9]. Recently, two new flavonoids; diosmetin glycoside and biflavone, were isolated and identified in G. verum L., in addition to isorhamnetin and its glycosides, kaempferol, quercetin, diosmetin and its glycosides [10,11].

Bedstraw species, including G. mollugo, also contain mollugin [7], flavonoids [8], coumarins, phenolic acids, and iridoid glucosides [12,13]. Some of these compounds have allelopathic, fungistatic, or repellent effects, and may also be used to flavour food or wine [14]. Recently, extracts from this plant were evaluated for their anti-cancer and anti-malarial activities and for their ability to inhibit HIV–1 reverse transcriptase, but initial results showed no activity [15].

The flora of Libya is not rich in the number of species; however, the Al-Jabal Al-Akhdar Mountain landscape comprises the richest vegetation and the highest number of species known from Libya [16]. The geographical affinity of the flora is mainly East Mediterranean rather than neighboring regions of North Africa [17,18].

In Libya, Rubiaceae is one of the eight species-rich families which represented by 50 genera and 90 species [19]. The genus Galium is represented by 10 species; G. mollugo L., G. spurium L., G. aparine L., G. tricornutum Dandy, G. verrucosum Huds., G. parisiense L., G. setaceum Lam., G. recurvum Req. ex DC., G. cossonianum Jafri, and G. murale (L.) All.

As from the beginning of 1990s, the increasing interest of molecular approach in taxonomic studies, especially those based on nucleic acids sequences, a remarkable decrease in number and importance of investigations dealing with chemotaxonomic evidence. Therefore, some authors urged this trend, and recommended research work on non-molecular evidences [20].

There is often confusion between different samples of this genus in herbariums and so the aim of this study is to develop a method to find characters providing data of both taxonomical and pharmaceutical use. No phytochemical studies were reported so far from Galium species in North African countries. The present work aims to establish foliar flavonoid patterns of five Galium species from Libya, in an attempt to determine chemical affinities among species and compare the results obtained with affinities indicated by evidences from morphology.

Materials and Methods

Plant material

Table 1 shows locations, types of habitats, dates of collection, GPS coordinates of localities, elevation and number of populations that were examined for the selected 5 species of Galium. Aerial parts of all plants were collected from natural populations. For each species at least two populations from distant habitats were studied. Altogether, 80 specimens were collected from their natural habitats in different locations of Libya. Voucher specimens of the studied species were deposited at the herbarium of Cairo University (CAI).