High‑Performance Liquid Chromatography‑Fingerprint Analyses, In vitro Cytotoxicity, Antimicrobial and Antioxidant Activities of the Extracts of Two Cestrum Species Growing in Egypt

Background: Cancer diseases and microbial resistance are serious health disorders associated with oxidative stress and infectious diseases. Their risks can be reducing via using polyphenols-rich plants. Methodology: Different solvent extracts from two Cestrum species (Cestrum nocturnum and Cestrum elegans) were evaluated for their biological and chemical activities. Also, the chemical profiles of the most promising extracts were investigated via high‑performance liquid chromatography (HPLC)‑fingerprint analyses. Results: The tested extracts showed weak to moderate cytotoxicity against Vero cell line with IC₅₀ values ranged from 133.67 μg/ ml to 57.634 μg/ml. The only noncytotoxic extractive fraction was the dichloromethane extract of C. elegans leaves with an IC₅₀ value of 204.732 μg/ml, while the most toxic extract was the ethyl acetate extract of C. elegans flowers with an IC50 value of 19.22 μg/ml. The antimicrobial activity results revealed that the n‑BuOH extract of C. nocturnum was the most active against four tested microbial strains with inhibition zones (10–13 mm). Also, the water and n‑BuOH extracts of C. elegans leave exhibited moderate activities with inhibition zones (7–9 mm), while for C. elegans flowers both of water and methanol extracts showed strong activities (9–14 mm). In the 2,2’‑diphenyl‑1‑picrylhydrazyl assay, the most active fraction was EtOAc with IC₅₀ values of 100.52 μg/ml and 64.40 μg/ml for C. elegans leaves and flowers respectively, while for C. nocturnum the most active fraction was methanol with an IC₅₀ value of 161.16 μg/ml, all relative to 7.60 μg/ml of ascorbic acid. HPLC‑fingerprint analyses revealed that the major identified compounds in the ethyl acetate extract of C. elegans flowers are caffeic acid, coumaric acid, vanillin, and rutin, while for the n‑butanol extract of C. nocturnum leaves are coumaric acid and vanillin. Conclusion: The obtained results revealed that the two species can be used as natural sources of antioxidant compounds with low cytotoxic effect on the mammalian cell line.