Antioxidant isolation and characterization from the plant Tradescantia spathacea Sw. of the Commelinaceae family

Abstract A novel bioactive flavan glycoside was isolated by solvent extraction method with the help of Soxhlet apparatus from the methanolic extract of Tradescantia spathacea Sw. Flavan glycoside having molecular formula C20H22O10, melting point 175-1780C, molecular weight by ESI-MS m/z (M + H]+ 423, optical rotation was[α]21D-45.1(c 0.20 methanol). Its structure was determined (–)-epicatechin 7-O-alpha-L-arabinopyranoside. Various color reactions, chemical degradation (like acid hydrolysis, permethylation, and enzymatic hydrolysis), UV-Visible spectrophotometry, Fourier transforms infrared spectroscopy, electrospray ionization mass spectrometry, and nuclear magnetic resonance spectroscopy were used to establish the structure of compound (–)-(–)-epicatechin 7-O-alpha-L-arabinopyranoside.. A flavan glycoside was also tested with a DPPH assay method for antioxidant activity by using Ascorbic acid as standard. DPPH radical scavenging test data demonstrate that a flavan glycoside possesses potent antioxidant activity so this flavan glycoside can be utilized as a potent antioxidant agent. Graphical Abstract


Introduction
Tradescantia spathacea Sw. is associated with the Commelinaceae family and it is usually famous as Moses-in-a-basket, Oyster plant, or Boat Lilly.This plant was discovered in Guatemala, southern Mexico, and Belize.The genus name honors John Tradescant, an English horticulture and plant collector.Because of its lovely leaves, it is extensively planted in tropical locations.It is widely cultivated in the West Indies.It is also a decorative plant.It has demonstrated intrusive characteristics by escaping gardens and naturalizing in portions of Louisiana and Florida.It has purple underside leaves.Over time, the plant will grow to produce a dense ground covering.Plants through white flowers in axillary cymes are surrounded by long-lasting.Moses in a basket bract is a boat-shaped purple bract.Its blooms bloom all year round.The current work intends to investigate anti-oxidant capabilities in methanolic extracts and chemical characterizations of isolated arabinoside (Kadam and Kakde 2017).
Medicinal plants are well-known for their antioxidant properties due to the presence of bioactive chemicals like phenols, benzoic acid, flavonoids, cinnamic acids, carotenoids, and folic acid (Moure et al. 2001;Cai et al. 2004;Balázs et al. 2013).T. spathacea, synonyms are Rhoeo spathacea or Rhoeo discolor; for the treatment of dysentery, haemoptysis, and blooms in China used as herbal tea of leave extract (Madaleno 2009).In another investigation, terpenoids, cardiac glycosides, phenolics, flavonoids, alkaloids, tannins, saponins, and steroid substances were identified in a T. spathacea extract of leaves (Parivuguna and Gnanaprabhal 2008).T. zebrina leaf extracts were analyzed for flavonoids, alkaloids, tannins, phenols, and steroids.T. Fluminense leaf extracts were found to include saponins, phenolic compounds, and flavonoids.These ancient applications may indicate the existence of potentially bioactive chemicals (in their chemical makeup) capable of preventing or treating specific ailments.Because scientific data is limited, such applications must be carried out using proper scientific methodologies.Current research has translated these ancient uses into possible current medical uses.The main known phytochemical substances in Tradescantia species include alkaloids, flavonoids, phenolic, and saponins (Alaba & Chichioco-Hernandez, 2014;Parivuguna & Gnanaprabhal, 2008;Wawer et al., 2017).The most prevalent flavonoids recognized include apigenin, luteolin flavonols, 6-hydroxy luteolin, and tricin (C-glycosides).Leaf extract of T. spathacea, the phytochemical investigation indicated the presence of coumarins, terpenoids, saponins, flavonoids, and alkaloids (Tan et al. 2014).Huq et al. (2016) performed a T. pallida preparation and were phytochemically screened, alkaloids, tannins, and carbohydrates were found in high, moderate, and insignificant concentrations correspondingly.Though, no detailed metabolites were extracted or recognized.T. spathacea contains many phenolic and carotenoid compounds that have been associated with anticancer and/or radical scavenging actions (Rosales-Reyes et al. 2008).Quoc Hung Vo et al. recognized four phenolic compounds (epigallocatechin, rhoeonoin, peltatoside) and rutin in T. spathacea leaves using HPLC-DADMS (Vo et al. 2015).Garca-Varela et al. conducted research using HPLC-DAD-TOF-MS (García-Varela et al. 2016), T. spathacea was found to have the following metabolites: rhoeonin (Ragragio et al. 2013).In this investigation, we isolated, characterized, and tested the antioxidant activity of a novel (-)-epicatechin 7-O-alpha-L-arabinopyranoside (Figure 1 Compound A).

Result and discussion
The compound has molecular formula The hydrolysate produced by the aqueous hydrolysis of compound A was neutralized through BaCO 3 and the BaSO 4 was filtered out.The filtrate was concentrated and chromatographed on paper, revealing the presence of L-arabinose (R f 0.53) (Kristiansen et al. 2010;Chemin et al. 2016).Chemical compound A confirmed that sugar is present in pyranose form.
Permethyalation of (Patil et al. 2015;Fabiana Meijon Fadul 2019) following acid hydrolysis of chemical compound A, methylated aglycone and methylated sugar is produced, demonstrating the existence of a hydroxy group in chemical compound A. The methylated aglycone was associated as 7-hydroxy-3,5,3′,4′-tetra-methoxy flavan which confirm the glycosidation was concerned at C-7-OH location of aglycone.The methylated sugar was recognized as 2, 3, and 4 tri-methoxy arabinoses (R G 0.84).Therefore it was determined that C-1′'' of L-arabinose was involved in the -OH group of the C-7 position of aglycone Enzymatic hydrolysis of Chemical compound A by almond emulsion reveals α-linkage of arabinose aglycone, and further hydrolysis of glycoside by Takadiastase enzyme reveals α-linkage of L-arabinose through aglycone.Chemical compound A was recognized as (-)-epicatechin 7-O-alpha-L-arabinopyranoside based on the information presented above (Asati and Yadava 2018).

Method and material
The melting points were all determined using thermoelectric melting point equipment.The FT-IR spectrum was documented on the Bruker alpha ATR spectrometer; UV spectra were measured in Methanol using a Lab India double bean spectrophotometer, and to record 1 H NMR spectra in DMSO-d 6 using a Bruker 500 MHz spectrometer.DMSO-d 6 was used to record 13 C spectra recorded using a Bruker at 125 MHz spectrophotometer (δ).Chemical shift readings were recorded in ppm units, while J values were described in Hz.The ESI-MS spectrum was measured on a water-XEVO-TQD#QCA1301 mass spectrometry instrument.

Plant material collection
The plant material was collected nearby the Bhopal and Sagar area.Taxonomically recognized by the taxonomist in the department of Botany at, Dr. H.S. Gour University, Sagar, India.A receipt sample copy (BOT/H/07/174/05/04) has been submitted to the Natural Products Laboratory, Department of Chemistry of this university.

Extraction and isolation
In the Soxhlet apparatus, air-dried powdered plants (4 kg) were extracted through methanol aimed at 6-8 days.The resulting methanol extract was concentrated at reduced pressure, yielding a brownish viscous mass that was partitioned through increasing polarity solvents, including petroleum ether, chloroform, ethyl acetate, acetone, and methanol.A rotatory evaporator was used to condense the methanol soluble fraction at a decreased pressure, yielding a dark viscous mass of 2.95 g.TLC analysis by silica Gel-G by nBAW (4:1:5) solution system and Iodine vapors as a derivatizing cause revealed one spot, suggesting that it was chemical A, It was then separated through column chromatography on a SiO 2 -gel G column using varying amounts of CHCl 3 : CH 3 OH (7:3).The solvents of the created eluents were separated and crystallized from the ether, providing chemical compound A (1.85 gm.).

Permethyalation of chemical compound A
Chemical compound A was solubilized in dimethylformamide (25 ml) and refluxed for 48 h through methyl iodide (5 ml) and Ag 2 O (35 mg), after which it was filtered and washed through dimethylformamide.After drying, the filtrate was hydrolyzed with 10% H 2 SO 4 to provide methylated aglycone 7-hydroxy 5, 3′, 4′-tetra-methoxy flavan.After extracting the aglycone, the aqueous hydrolysate was neutralized with BaCO 3 and BaSO 4 before being filtered.The filtrate was dehydrated in a vacuum rotatory evaporator before being submitted to paper chromatography using an nBAW (4:1:5) solvent combination and aniline hydrogen phthalate as a visualizing agent.The methylated sugars were recognized as 2, 3, and 4-tri-methoxy arabinose (R G 1.10).

Enzymatic hydrolysis of chemical compound A
Chemical compound A (35 mg) was solubilized in methanol (25 ml) and digested by an equivalent quantity of Takadiastase enzyme, releasing -L-arabinose (R f 0.53) and indicating α-linkage along the aglycone.After that hydrolysis of glycoside through the almond emulsion, indicates the α-linkage of L-arabinose (R f 0.53) among aglycone.

Antioxidant activity of chemical compound A
The DPPH test was used to determine chemical compound A's free radical scavenging activity (Nath and Asati 2018).3 ml of DPPH solution (0.1 mM) was combined through 2 ml of each chemical solution (5-100 μg/ml) and incubated in the darkroom for 30 min.After 30 min of incubation, the absorbance of the DPPH solution was recorded at 517 nm in comparison to the blank.As a control, 99% methanol was used.The DPPH solution and methanol are present in the control solution.Ascorbic acid was chosen as the gold standard (Table S1, Figure S10, and Table S2, Figure S11).

Conclusion
Based on the data presented above, the structure of compound A was determined to be (-)-epicatechin 7-O-alpha-L-arabinopyranoside, which demonstrated considerable antioxidant activity and, has the potential to be utilized as a robust anti-oxidative source.
The following equation was used to compute the percentage of inhibition of the DPPH free radical.-% Inhibition = (Ao-As/Ao)