Phytochemical profiling of Clerodendrum speciosum leaves and evaluation of their antioxidant, antihyperglycemic and antiarthritic activities in vitro

Background

Clerodendrum speciosum is a hybrid of C. thomsonae and C. splendens. Many biological and phytochemical studies have been performed on C. thomsonae and C. splendens, but few studies have been conducted on C. speciosum. Its methanol extract previously showed antioxidant activity in vivo via Caenorhabditis elegans model owing to its richness in flavonoids and phenylpropanoids.

Results

Characterization of C. speciosum leaf volatile constituents (CSV) was performed via gas chromatography linked to mass spectrometry (GC–MS). This revealed the presence of 29 metabolites that belonged mainly to oxygenated monoterpenes, sesquiterpenes and their oxygenated compounds, fatty acids and their esters. The latter constituted the predominant metabolites, whereas linoleic acid (30.64%) is the major metabolite. Liquid chromatography linked to mass spectrometry (LC–MS) was performed on the ethyl acetate fraction of C. speciosum leaves (CSE). This resulted in a tentative assignment of twenty-four peaks, whereas six peaks were not identified. These identified metabolites mainly belonged to phenylpropanoids, whereas flavonoids, iridoid glycosides, phenolic acids and their derivatives were also detected. The leaf volatile constituents showed notable antiarthritic activity as evidenced by the significant inhibition of albumin denaturation with an IC₅₀ of 32.50 μg/mL comparable that of diclofenac sodium (15.12 μg/mL). The leaf ethyl acetate fraction revealed potent antioxidant effect estimated by 725.43 ± 5.95 mg TE/g, 333.82 ± 19.9 mg TE/g, 2.1 ± 0.08 mmol TE/g and 3.69 ± 0.3 mg EDTA/g. in cupric-reducing antioxidant capacity (CUPRAC), 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), phosphomolybdenum (PHD) and metal-chelating activity (MCA) assays, respectively. It showed a reasonable α-glucosidase and α-amylase inhibition estimated by 1.88 ± 0.05 and 0.14 ± 0.01 mmol ACAE/g, respectively. ADME/TOPAKT assessment, processed on the prevalent identified components detected in CSV, displayed acceptable pharmacodynamic, toxicity and pharmacokinetic behaviors for most tested compounds except for n-nonadecane and n-heptacosane and n-octacosane.

Conclusion

Thus, C. speciosum leaves could serve as a promising treasure for the treatment of many diseases such as arthritis and diabetes mellitus owing to its abundance with flavonoids and terpenoidal compounds.