Sodium borohydride

Ferrous chloride tetrahydrate
(FeCl₂·4H₂O), ascorbic acid (C₆H₈O₆), sodium borohydride (NaBH₄), hydrochloric acid (HCl), potassium iodide (KI), sodium hydroxide
(NaOH), and acetic acid (CH₃COOH) were purchased from Merck.
Arsenic standard solution 1000 mg/L for AA (arsenic III-oxide in 0.5
M nitric acid solution, d = 1.01 g/cm³) was purchased from Scharlau, Spain. Ammonium hydroxide (NH₄OH) was obtained from Macklin-China, India. The red mud was
from Central Highlands, Vietnam (particle size ≤200 μm;
main components include Al₂O₃:14.0%, CaO: 2.3%,
Fe₂O₃: 55.5%, SiO₂: 5.3%, and MKN:
11.1%). All chemical solutions were diluted with distilled water until
the desired concentration was reached.

Ascorbic acid (AA or AAH^-), silver nitrate (AgNO₃), cetyltrimethylammonium bromide (CTAB), sodium borohydride (NaBH₄), 2-(n-morpholino) ethane sulfonic acid (MES), ethylenediaminetetraacetic acid iron(III) sodium salt (iron(III) edta), 5-bromo-2-hydroxybenzoic acid (5-BrSA), hydrogen peroxide (H₂O₂) (to standardize H₂O₂, it was quantitatively oxidized by titration with potassium permanganate), and hydrogen tetrachloroaurate (HAuCl₄) were purchased from Sigma‒Aldrich. For all of the experiments, we used deionized water (18.2 MΩ) for solution preparation.

G. cochinchinense plants were collected from Bach
Ma, Thua Thien Hue province, Vietnam, and identified by the Department
of Biology, College of Sciences, Hue University. A voucher specimen
(Code: BM2022.06) was deposited at the Department of Chemistry, Hue
University of Sciences, Hue University.
Sephadex G-100, dimethyl
sulfoxide ((CH₃)₂SO, DMSO), dimethyl sulfate
((CH₃)₂SO₄), sodium borohydride (NaBH₄), 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic
acid) diammonium salt (ABTS), gallic acid (GA), ascorbic acid (AS),
sodium nitrate, dimethyl sulfoxide (DMSO), and trifluoroacetic acid
(TFA) were procured from Sigma-Aldrich Co. Diethylaminoethyl cellulose-52
(DEAE-cellulose-52), H₂SO₄, ammonium molybdate,
sodium phosphate, and a Thermo Fisher Dialysis membrane (M_w cutoff 8000–14,000 Da), were bought from Bum
Han Commercial Co. Acetylcholinesterase (AchE), acetylthiocholine
Iodid (ACTI), 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB), sodium
nitrite, sulfanilamide, and N-1-naphthyl ethylenediamine
dihydrochloride were bought from Sigma Chemical Co. (St. Louis, MO).
All utilized reagents and solvents were of analytical grade and strictly
adhered to quality standards.
The HepG2, A549, KB, and MCF-7
cancer cell lines were supplied
by Long Island University and the University of Milan. These cell
lines were cultivated in appropriate culture media supplemented with
10 % fetal bovine serum (FBS) and essential ingredients. Culturing
procedures were strictly carried out under sterile conditions with
5 % CO₂, maintained at 37 °C and 98 % humidity.
The gas chromatography - Flame Ionization detector (GC-FID) was
operated under the following conditions: hydrogen gas, air gas, and
nitrogen carrier gas. The injection volume was set to 1 μL,
and the probe temperature was maintained at 300 °C. The analytical
column used was DB-17HT, measuring 30 m in length, 0.25 mm in internal
diameter and 0.15 μm in film thickness.
The gas chromatography-mass
spectrometry (GC-MS) parameters were
as follows. Helium was the carrier gas at 13 psi, with 1 μL
sample volume injected at a 20:1 split ratio and an injection temperature
of 250 °C. The temperature was program started at 150 °C,
increased by 10 °C per min to 280 °C, and was held for 5
min. The MS conditions included an ionization energy of 70 eV, an
interface temperature of 280 °C, a source temperature of 230
°C, and a quadrupole temperature of 150 °C.
The Fourier
transform infrared (FT-IR) spectra were recorded by
using an IRPrestige-21 spectrometer. A sample was prepared by thoroughly
grinding and pressing a mixture of dried polysaccharide (PS) powder
(2 mg) and potassium bromide (KBr) powder into pellets with a thickness
of 1 mm. The measurements were performed across a spectral range of
4000–400 cm^–1 with a resolution of 8 cm^–1.
Nuclear magnetic resonance (NMR) spectroscopy
of the polysaccharide
solution was acquired using a Bruker AM500 FT-NMR spectrometer at
500 MHz for ¹H and 125 MHz for ¹³C nuclei at
353 K. Parameters were set at 1.00 s delay (Dl) and 3.28 s acquisition
time (AQ) for ¹H NMR, and 2.0 s delay and 1.1 s acquisition
time for ¹³C NMR. Two-dimensional spectra (Heteronuclear
Single Quantum Coherence spectroscopy (HSQC), heteronuclear multiple
bond correlation (HMBC), and nuclear overhauser enhancement spectroscopy
(NOESY)) were used to elucidate sugar residues, with chemical shifts
reported in ppm.