Effect of frequency, temperature, and time of sonication on xanton content of mangosteen (Garcinia mangostana L.) peel extract through ultrasound assisted extractionSuryono Suryono, Hadiyanto Hadiyanto, Moh. Yasin, Retno Widyowati, Muflihatul Muniroh and Annisa` AmaliaE3S Web Conf., 125 (2019) 25006DOI: https://doi.org/10.1051/e3sconf/201912525006