Abstract:
Vetiver grass (Chrysopogon zizanioides;CZ) is a well-known grass that can both remediate
various heavy metals in soil as well as producing essential oil that is commonly used in premier
perfumery, food and pharmaceutical industries. Due to this versatility property, this study was
aimed at extracting essential oil from Chrysopogon zizanioides roots cultivated in SelibePhikwe mine tailings and study the quality and quantity (chemical composition and yield) of
the Chrysopogon zizanioides essential oil in relation to toxic multi heavy metals absorbed by
the grass assisted by Arbuscular Mycorrhizal Fungi (AMF) and ethelene Diamine Tetra-Acetic
Acid (EDTA) chelating agent. The experimental set-up was designed in a complete randomized
design with triplicates. The ultrasonic -assisted hydro distillation (UAHD) extracted CZ
essential oil was analysed in each treatment using Gas Chromatography Flame Ionization
Detector (GC-FID). Cumulatively fifty-nine constituents were identified from the seven
treatment samples, however few constituents which mostly were in trace amount were not
identified since they were not reported in similar studies. The essential oil was found to contain
mainly sesquiterpenes class of compounds. Control, T1, T2, T3, T4, T5, T6 shows the total
identified oils as 99.5%, 97.0%, 100%, 94.6%, 100%, 98.1% and 97.2% respectively. The
predominating constituents are alcohols (>50%) across all the treatments. The principal
constituents vary in all the treatments but the ‘finger print’ constituents; khusimol, ά-vetivone,
β-vetivone appears in > 50% of the treatment samples. The percentage yield ranged between
0.26% to 0.95%. Two factor ANOVA in complete Randomised Design showed that
statistically, the percentage yields across all the treatments are very highly significant (P
=0.000, P < 0.05).
Microwave acid assisted digestor (MAAD) was used to extract heavy metals from raw CZ roots
and extracted essential oil and The heavy metal analysis by Inductively Coupled Plasma
Optical Emission Spectrometer (ICP-OES) showed that across all the six treatments with CZ
grass grown in mine tailing containing multi heavy metals, the accumulation level is as follows:
Ni>Cu>Mn>Zn>Pb>As for raw CZ roots but the cumulative essential oil contained low to
negligible amount of heavy metals, as the concentration were; Cu (0.150 ± 0.007 mg kg-1
), Ni
(0.063 ± 0.001 mg kg-1
), Pb (0.022 ± 0.002 mg kg-1
), As (0.003 ± 0.003 mg kg-1
), Zn (0.109 ±
0.002 mg kg-1
), Mn (0.043 ± 0.001 mg kg-1
). It shows that the heavy metals were not co extracted with essential oil. There has been a significant increase in the number of constituents
produced by CZ grass for the treatments with CM only and inoculation of AMF with 5 mmol
EDTA single and a significant decrease for treatments with AMF and 5 mmol EDTA split,
EDTA single, 5 mmol EDTA split as well as AMF only as a result of high metal stress and low
metal respectively. The results showed that the amount of heavy metal content does not all the
time and it’s not the only factor influencing the production of chemical constituents. The
integrated effect of Ni, Cu, Mn, Zn, Pb and As in overall did not significantly alter the essential
oil composition of most of the CZ constituents across most of the treatments as compared to
the control treatment since precision was high.
The extracted light brown viscous CZ essential oil showed percentage yield of 0.26% (C),
0.36% (T3), 0.54% (T5), 0.86% (T1), 0.94% (T6) and 0.95% (T2). The trend shows that T1,
T2, T4, T6 had precise and better yield while for C, T3 and T5 the yields dropped with C being
the least. The treatments with no heavy metals nor AMF + EDTA (C), the yield was low due
to no or less metal stress triggering the production of essential oils.
Trinity, K (2024). The effects of heavy metals on the quality and yield of vetiver grass (chrysopogon zizanioides) essential oil. Afribary. Retrieved from https://afribary.com/works/the-effects-of-heavy-metals-on-the-quality-and-yield-of-vetiver-grass-chrysopogon-zizanioides-essential-oil
Trinity, Kereeditse "The effects of heavy metals on the quality and yield of vetiver grass (chrysopogon zizanioides) essential oil" Afribary. Afribary, 12 Apr. 2024, https://afribary.com/works/the-effects-of-heavy-metals-on-the-quality-and-yield-of-vetiver-grass-chrysopogon-zizanioides-essential-oil. Accessed 15 Oct. 2024.
Trinity, Kereeditse . "The effects of heavy metals on the quality and yield of vetiver grass (chrysopogon zizanioides) essential oil". Afribary, Afribary, 12 Apr. 2024. Web. 15 Oct. 2024. < https://afribary.com/works/the-effects-of-heavy-metals-on-the-quality-and-yield-of-vetiver-grass-chrysopogon-zizanioides-essential-oil >.
Trinity, Kereeditse . "The effects of heavy metals on the quality and yield of vetiver grass (chrysopogon zizanioides) essential oil" Afribary (2024). Accessed October 15, 2024. https://afribary.com/works/the-effects-of-heavy-metals-on-the-quality-and-yield-of-vetiver-grass-chrysopogon-zizanioides-essential-oil