Antioxidant Properties and Enzyme Inhibitory Activities of Eminium rauwolffii: LC-MS/MS-Based Polyphenolic Profiling

Eminium rauwolffii (Blume) Schott var. rauwolffii is a member of the Araceae a large and mainly tropical family distributed worldwide. The Eminium species are utilized for various purposes including therapeutic uses in traditional medicine and as food. To analyze the antioxidant properties of water extract of E. rauwolffii (WEER) and ethanol extract of E. rauwolffii (EEER), 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS^•+) radical and 1,1-diphenyl-2-picrylhydrazyl (DPPH^.) free radical scavenging, Fe³⁺-2,4,6-tris(2-pyridyl)-S-triazine (TPTZ) and Cu²⁺ reducing assays were studied. Antioxidant activities and reducing properties of both extracts were compared to standard antioxidants: BHT, BHA, α-Tocopherol, and Trolox. The IC₅₀ values of EEER for radical scavenging were higher than those of standard antioxidants (25.35 ± 1.42 μg/mL for ABTS^•+ and 106.80 ± 1.88 μg/mL for DPPH^•). The total phenolic and flavonoid quantities in WEER and EEER were measured in the range of 189.78 ± 0.01 to 298.54 ± 0.01 mg GAE/g and 89.37 ± 0.01 to 178.95 ± 0.01 mg QE/g, respectively. The IC₅₀ values for EEER and WEER against α-glycosidase, acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and carbonic anhydrase I and II (hCA I and II) enzymes were 10.79 ± 5.61 to 13.18 ± 5.77, 36.14 ± 4.61 to 62.63 ± 1.67, 69.37 ± 7.36 to 37.48 ± 0.27, 81.30 ± 5.95 to 62.35 ± 8.03, and 29.34 ± 1.38 to 115.90 ± 3.3 µg/mL respectively. The antioxidant activity and enzymes inhibitory capacity of WEER were close, and comparable to the capacity demonstrated by the standards. The amount of sixteen compounds was identified from EEER. Numerous phytochemicals, including cynaroside, p-coumaric acid, cosmosiin, caffeic acid, and quinic acid, were quantitatively determined using the LC-MS/MS method. This clearly indicates that phenolic- and flavonoid-rich E. rauwolffii may have potential in the management of glaucoma, Alzheimer's disease, diabetes, cardiovascular, and cancer disorders.