Studi inhibisi bromelain dari bonggol nanas (ananas comosus [l.] merr) hasil pemurnian kromatografi penukar ion dengan penambahan PCMB dan EDTA serta uji in vitro aktivitas antiplateletnya = Study of bromelain inhibition from pineapple core (ananas comosus [l.] merr) purified product using ionic exchange chromatography with addition of PCMB and EDTA and antiplatelet activity in vitro test