Jatropha’s Hidden Arsenal: A Natural Source for Bio-Pesticides and Medicine
Introduction
While Jatropha curcas has earned its fame as a leading biofuel crop, its true potential extends far beyond energy production. The seeds and the residual cake left after oil extraction are a treasure trove of potent bioactive compounds. This chemical arsenal, developed by the plant for its own defense, holds immense promise for agriculture and medicine.
The following excerpt from Dr. Abdul Haq’s doctoral research investigates the remarkable antifungal, antioxidant, cytotoxic, and enzyme-inhibiting properties of Jatropha extracts. It uncovers a world of possibilities, from developing natural pesticides to protect our crops to identifying novel compounds for anti-cancer and anti-diabetic research.
Excerpt
“In this study, the antifungal, antioxidant, enzyme inhibitory (α-amylase), phytochemical and cytotoxicity profile of seed oil and de-oiled seed cake extracts of Jatropha curcas, a multipurpose plant with huge potential of biofuel production and medicinal purposes, was determined.
The antifungal activities were investigated against the phytopathogenic fungal strains including Colletotrichum coccodes, Pythium ultimum, Phytophthora capsici, Rhizoctonia solani, Bipolaris oryzae and Fusarium fujikuroi.
Methanolic extract was found to be highly fungicidal as compared to aqueous and n-hexane extracts, and seed oil against P. capsici and F. fujikuroi strains. Methanolic extract was also found to possess significantly higher antioxidant potential (p<0.05) than others.
Conversely, seed oil was found to be rich in cytotoxic phytochemicals and exhibited significantly higher (p<0.05) α-amylase inhibitory activity while remained more cytotoxic against brine shrimps than n-hexane, methanolic and aqueous extracts. Methanolic extract was found to possess significantly higher content of total phenolics and flavonoids (p<0.05) than the seed oil and other extracts.
These results indicated that J. curcas seed oil and its various extracts can be further investigated for their antimicrobial potential and as competent bio-pesticides.
Traditionally, different parts of J. curcas plant have been used for the treatments of skin infections, dysentery, fever, coated tongue, gonorrhea, inflammation and rheumatoid arthritis (Hassan et al., 2004). Its stem bark, latex, leaves and de-oiled seed cake have vastly been reported for their antibacterial, antifungal, antiviral, cytotoxic, antioxidant and anti-molluscidal activities in vitro (Srinivasan et al., 2019).
The seeds possess certain compounds such as phorbol esters, curcin and trypsin inhibitors, which make this plant a potential candidate for medicinal uses (Srinivasan et al., 2019). However, the antifungal activities of J. curcas plant have mostly been carried out against human pathogenic fungal strains. On the other hand, plant fungi are the main pathogens that cause a considerable loss to yields in agricultural crops.
Antifungal Activities
In this study, methanolic extract of de-oiled seed cake exhibited higher antifungal activities (MICs) as compared to seed oil and n-hexane and aqueous extracts against P. ultimum, P. capsici, R. solani, B. oryzae, F. fujikuroi. Generally, methanolic extract of medicinal plants have been reported to exhibit higher antifungal activity when compared to that of aqueous or n-hexane extract due to its higher antimicrobials extraction capability (Khan et al., 2018).
The methanolic extract also exhibited MFCs at 3.1 and 6.3 mg/mL against P. capsici and F. fujikuroi, respectively. The seed oil only exhibited MFC at 12.5 mg/mL against F. fujikuroi strain, while the aqueous and n-hexane extracts did not exhibit any MFCs against any strain. The high antifungal potential of methanolic extract strengthens its traditional use as antiseptic (Abdelgadir and Van Staden, 2013) and also as a drug of choice for the control of crop diseases.
Antioxidant Activities
The DPPH scavenging of free radicals is correlated to antioxidant potential of medicinal plants. The free radicals are the reactive oxygen species that are produced in response to an injury or after the digestion of certain foods (Lobo et al., 2010). The excess of free radicals in cellular environment may cause oxidative stress which sometime may lead to cell’s damage/decay. The de-oiled seed cake extracts and seed oil exhibited DPPH scavenging activities in concentration dependent manner.
The methanolic extract exhibited significantly higher scavenging activity as compared to the seed oil, n-hexane and aqueous extracts. Based on IC₅₀ values, the antioxidant activity of methanolic extract was significantly higher (p<0.05) than the aqueous and seed oil and non-significantly higher than the n-hexane extract.
Alpha Amylase Inhibition
Alpha amylase is an important enzyme used in the conversion of carbohydrates into glucose during metabolism. Therefore, it is considered as the main agent for liberation and increase in the after-meal blood glucose level in diabetic patients (Des Gachons and Breslin, 2016).
If the alpha amylase enzyme is inhibited it can stop the release of high-level glucose in blood to avoid accumulation of keto-acids in the body (Kazeem et al., 2013). Currently, inhibition of amylases is considered an area of high interest in diabetes research (Dineshkumar et al., 2010). The highest percent amylase inhibitory activity was exhibited by J. curcas seed oil followed by methanolic, n-hexane and aqueous extract.
Cytotoxicity on Brine Shrimp
Cytotoxic activity using Brine shrimp lethality is a simple assay which can be used to assess the cytotoxic activity of a compound (Apu et al., 2013). The results indicated that the cytotoxic activities of J. curcas de-oiled seed cake extract and seed oil against brine shrimps were concentration dependent. The cytotoxic activity of J. curcas seed oil was significantly higher (p<0.05) than n-hexane, aqueous and methanolic extract.
The LD₅₀ values show that seed oil (LD₅₀: 0.08 mg/mL) had exhibited significantly (p<0.05) higher mean cytotoxic activities than n-hexane (LD₅₀: 0.14 mg/mL), aqueous (LD₅₀: 2.83 mg/mL) and methanolic (LD₅₀: 5.69 mg/mL) extracts against brine shrimps. The compound with lowered LD₅₀ value can be used as an alternative potent source of anti-cancer and pesticide drugs.”
Source Citation
- Researcher’s full name: Abdul Haq
- Title: Biotechnological Applications of Jatropha curcas Seeds for Bioenergy Carriers and Bioactive Compounds
- Guide(s): Dr. Malik Badshah
- University: Quaid-i-Azam University, Islamabad
- Completed Date: 2020
- Excerpt Page Numbers: 112, 113, 114, 123, 124, 126, 128, 129
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