Effect of reverse osmosis concentration coupled with drying processes on polyphenols and antioxidant activity obtained from Tectona grandis leaf aqueous extracts

• Powders of aqueous extract from Tectona grandis leaf were obtained at pilot scale processes.
• Effect of processes on phenolic compounds and antioxidant activity were studied.
• Polyphenol contents were identified and characterized by LC–MS.

Tectona grandis leaf extracts obtained at pilot scale processes (ultrasound-assisted extraction, cross-flow microfiltration, reverse osmosis concentration) contains phenolic compounds that exhibit antioxidant properties. The final reverse osmosis concentrate extract presented higher content of polyphenol (21,080 ± 117 μmol g−1 GAE) and antioxidant capacity (8490 ± 29 μmol g−1 TE) comparatively to crude extract (1300 ± 12 μmol g−1 GAE for polyphenol and 430 ± 2 μmol g−1 TE for antioxidant activity) or cross flow microfiltration extract (1170 ± 10 μmol g−1 GAE for polyphenol and 400 ± 10 μmol g−1 TE for antioxidant). The concentration factors of polyphenol and antioxidant capacity were 18 and 21, respectively. High-performance liquid chromatography (HPLC) coupled to electrospray ionization mass spectrometry (ESI-MS) detection negative ion mode has been used to identify and characterized polyphenols in the concentrate extract of T. grandis leaves. Seven phenolic acids and flavonoids were characterized. Verbascoside (phenolic acid) was described as the most abundant phenolic compounds in this concentrate extract. Two drying technologies (freeze-drying and spray-drying) were used to obtained stable powder from concentrate extract. The effect of these drying technologies on phenolic compounds and antioxidant activity were studied. Freeze-drying presented a good recovery of phenolic compounds and antioxidant capacity. This drying technology could be used for preservation of T. grandis extract.