The authors are grateful to the Graduate School of Chulalongkorn University and the Ratchadaphiseksomphot Endowment Fund of Chulalongkorn University (RE 556053018-FW) (to ST) for partially supporting this project. We also thank Ms. Suttira Khumkratok, Walai Rukhavej Botanical Research Institute, Mahasarakham University, Mahasarakham 44000,
Thailand for identification and deposition of the plant material.