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Laticifers identification and natural rubber characterization from the latex of Periploca angustifolia Labill. (Apocynaceae)

Dghim, Fairouz, Bouaziz, Mohamed, Mezghani, Imed, Boukhris, Makki, Neffati, Mohamed
Flora 2015 v.217 pp. 90-98
Apocynaceae, chemical analysis, forage, latex, leaves, livestock, mastication, mesophyll, molecular weight, pericarp, periderm, rubber, shrubs, taste
Periploca angustifolia (Apocynaceae) is a multipurpose shrub widely distributed in arid and semi-arid Tunisian regions. Local people often use this laticiferous shrub us a fodder for their livestock and consume the dried latex as a pleasant taste chewing. This study aims to identify laticifers distribution in vegetative and reproductive organs of Periploca angustifolia and investigate latex composition in order to valorize this constituent for later use. The histological study conducted on this species has confirmed the presence of laticifers in leaf (spongy and palisade mesophyll), stem (cortical parenchyma), root (periderm), floral bud (petal–carpel) and follicle (pericarp). Laticifers in the studied species are non-articulated. The purified rubber fraction from latex was subjected to different chemical analyses, proving that the rubber of P. angustifolia is composed of cis-1,4-polyisoprene as the main constituent. When the molecular weight distribution of rubber components in the exudate was measured using SEC analysis, the number-average molecular weight (Mn), the weight-average molecular weight (Mw), and polydispersity (Mw/Mn) were estimated to be Mn=2.3×105, Mw=4.1×105 and Mw/Mn=1.78, respectively. Thus, the obtained results show that the latex of P. angustifolia contains a natural rubber.