Abstract Background The systematic screening of plant species with the purpose of discovering new bioactive compounds is prerequisite for any bioprospecting study. Therefore the present study was carried out to assess the phytochemical content and the evaluation of in vitro antioxidant, antibacterial, larvicidal and antidiabetic activities of the methanol extracts of S.caryophyllatum bark, leaves, fruit pulp and seeds. Methods The quantitative estimation of total phenol, flavonoid and tannin content of the extracts of S. caryophyllatum bark, leaf, fruit pulp and seeds were analyzed by using standard methods. The present study also conducted to screen antioxidant (DPPH, ABTS assays), antimicrobial, antidiabetic (in vitro α-amylase and α-glucosidase inhibitory assays) and larvicidal (against fourth instars larvae of Aedes aegypti and Culex quinquefasciatus) activities of methanol extract of S. caryophyllatum. Results The results of quantitative phytochemical analysis revealed the presence of maximum amount of phytoconstituents such as phenol, flavonoids and tannins in the leaf, bark and seed extract when compared to fruit pulp extracts. Free radical scavenging activity indicated that methanol bark, leaves, fruit and seeds extracts has significant free radical scavenging ability on DPPH with percentage inhibition of 88.15%, 81.31%, 75.24% and 83.36% respectively. The in vitro α-amylase and α-glucosidase inhibitory studies of the methanol crude extracts of four different plant parts of S. caryophyllatum (Bark, leaf fruit pulp and seed) showed good inhibitory activities in concentration dependent manner. The maximum percentage inhibitory activity of 78.03% was showed at concentration of 500 μg/ml seed extracts followed by bark (78.03%), leaf (69.4%) and fruit pulp (56.9%) at the same concentration. While the percentage inhibitory activity of four extracts also showed potent inhibition of α-glucosidase; maximum inhibition exhibited at the concentration of 100 μg/ml by bark extract (80.9%) compared with other extracts, leaf (78.2%), seed (77.59%) and fruit pulp (63.35%). The leaf essential oil and four extracts showed significant mortality against fourth instars larvae of Ae. aegypti and Cx. quinquefasciatus respectively. Conclusion Thus the present study suggests that S.caryophyllatum plant parts can be used as natural antioxidant source to prevent diseases associated with free radicals. Also, this plant can be a good source for further purification studies for isolation and characterization of compounds related to these antioxidants, antidiabetic and antibacterial activities.