Title:Non-Alkaloidal Compounds from Tubers of Gloriosa superba and their In
vitro and In silico Antibacterial and Antioxidant Activities
Volume: 19
Issue: 8
Author(s): Tsegu Kiros, Rajalakshmanan Eswaramoorthy, Seid Mohammed, Aman Dekebo*Yadessa Melaku*
Affiliation:
- Applied Chemistry Department, School of Applied Natural Sciences, Adama Science and Technology University, Adama,
1888, Ethiopia
- Institute of
Pharmaceutical Sciences, Adama Science and Technology University, Adama, Ethiopia
- Applied Chemistry Department, School of Applied Natural Sciences, Adama Science and Technology University, Adama,
1888, Ethiopia
Keywords:
Gloriosa superba, tuber, non-alkaloid, antibacterial activity, antioxidant activity, docking study.
Abstract:
Background: The tubers of Gloriosa superba L. (Colchicaceae) are previously well known
for their alkaloidal constituents. The present work aimed to investigate the non-alkaloidal constituents
and evaluate their in vitro and in silico antibacterial and antioxidant activities from the tuber.
Methods: The chloroform: methanol (1:1) tuber extract was fractionated over silica gel column
chromatography, and isolated compounds were characterized by NMR spectroscopy. Various extracts
and isolated compounds were evaluated for their antibacterial and antioxidant activities
against certain pathogenic strains and oxidants. The in silico drug-likeness properties of isolated
compounds were also studied against 6F86 antibacterial and 1HD2 antioxidant protein models.
Results: Three non-alkaloidal compounds, β-sitosterol (1), 3-(cyclopenta-2,4-dienyloxy) β-
sitosterol (2) and 1,2-n-dipropyl phthalate (3), were reported herein. The n-hexane and chloroform
extracts displayed better antibacterial activity against E. coli (9.83 ± 0.28 mm) and P. aeruginosa
(10.65 ± 0.79 mm), and S. aureus (10.33 ± 0.3 mm), respectively, at 100,000 μg/mL concentration.
Compound 3 established a better activity against all bacterial strains (9.78 ± 0.63-11.07 ± 0.09 mm)
at 1000 μg/mL (IC50 values of 1.5-3.2 μg/mL). All the extracts exhibited a DPPH free radical scavenging
activity comparable to ascorbic acid (IC50 value of 1.2 μg/mL), whereas isolated compounds
were found with negligible DPPH scavenging activity and weak ferric ion reduction power up to
500 μg/mL dose. The docking study revealed that all the compounds fulfilled Lipinski’s rule of five
by contravening no more than one rule with strong binding affinity shown by compound 1 (-8.2
kcal/mol) and compound 3 (-4.5 kcal/mol) to the 6F86 bacterial and 1HD2 antioxidant protein
models, respectively, which are comparable to the ciprofloxacin (-7.2 kcal/mol) and ascorbic acid (-
4.5 kcal/mol) drugs. All the compounds also did not show any cytotoxicity properties. Whereas
compound 1 showed an immunotoxicity and mutagenicity properties; and compounds 2 and 3 were
found as immunotoxic and carcinogenic isolates, respectively.
Conclusion: The promising antioxidant activity result of the various tubers extracts may highlight the
potential use of Gloriosa superba as a source of foods by conducting further phytochemical investigation
and additional bioassay evaluation, including the cytotoxicity effect of the whole part of the plant.
