Methanol extracts from S. jambos leaves were tested for antimicrobial activity and toxicity. S. jambos leaf extract inhibited the growth of 4 of the 14 bacteria tested (29%). Both gram-positive and gram-negative bacterial growths were inhibited by S. jambos leaf extract, although gram-positive bacteria appeared more susceptible. Two of the 10 gram-negative bacteria (20%) and 2 of the 4 gram-positive bacteria (50%) tested had their growths inhibited by the extract. The leaf extract also proved to be toxic in the Artemia franciscana bioassay, with a 48-h LC 50 of 387.9 ± 38.8 µg/mL, making it slightly more toxic than Mevinphos (505.3± 37.7 µg/mL) and approximately 5-fold less toxic than potassium dichromate (80.4 ± 4.3 µg/mL). Whilst potassium dichromate's LC 50 remained constant across the 72-hour test period (24-h LC 50 , 86.3 ± 5.1; 72-h LC 50 , 77.9 ± 4.9), the extract and Mevinphos LC 50 values decreased by 72 hours (87.0 ± 11.3 µg/mL and 103.9 ± 12.8 µg/mL, respectively), indicating their similar levels of toxicity in the assay.