Plant material
The leaves of O. sessiliflora were collected at Parque Ambiental de Teresina, Piaui State, Brazil in June 2009. The plant authentication was performed by Professor Roseli Farias Melo Barros and a voucher specimen (TEPB 27870) has been deposited at Herbario Graziela Barroso do Amaral (UFPI).