Characterization of cork features of Erythrina mulungu and Enterolobium gummiferum in view of a potential valorization and conservation of forest species in the Cerrado bioma

The cork in the Cerrado endemic species Erythrina mulungu and Enterolobium gummiferum was characterized here for the first time in relation to structure and anatomical and chemical features, aiming to reconcile Cerrado native species conservation with income generation for local communities through a sustainable forest management. Both barks showed only one circumferential continuous periderm with a substantial cork layer featuring cork rings and characterized by deep longitudinal fractures originating from stem radial growth. The cellular features of both corks agree with the general characteristics of cork tissues regarding arrangement, topology and dimensions. However, in E. gummiferum the earlycork cells appeared radially stretched and with broken cell walls giving rise to higher tissue heterogeneity. Chemically, the corks of E. mulungu and E. gummiferum are characterized by a very high content in extractives (38.4% and 20.3% respectively), a low suberin content (4.7% and 3.9%, respectively), and high lignin content (36.8% and 38.6%, respectively). The ethanol-water extracts showed a low total phenolics content (27.0 and 32.2 mg GAE/g extract respectively). The cellular features confer to the corks of both species protective insulating properties that are important adaptative characteristics to the Cerrado environment. As regards potential applications, the corks may be used in insulation products with low mechanical resistance requirements, while the high content in polar extractives is indicative of a possible extraction pathway for added value compounds although further compositional and activity studies are needed.