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Dendrophthoe falcata is a partial stem parasite belonging to Loranthaceae
family, which is considered as a destructive pest of many economically important fruit
trees such as mango, sapota, sugar apple and guava. They cause damage to the host
plants by depleting nutrients, releasing toxins, and limiting their growth. Though
several management strategies have been suggested by previous researchers which
include pruning of its branches, base banding using 2,4-D and spray of ethrel in
combination with organosilicone (non-ionic surfactant), the latter gave a promising
response in comparison to others without affecting the host. Because of its destructive
nature, some of the potential pharmaceutical features of the parasite often go unnoticed;
if prospectively exploited it will automatically open up avenues for targeted removal of
the parasitizing aerial parts of D. falcata.
Plants are thought to be one of the most important sources for discovering and
developing pharmaceuticals that are both effective and safe compared to currently
available synthetic drugs. Traditional and folk medicines are gaining favour over
contemporary therapy due to fewer side effects and a higher safety margin.
Dendrophthoe falcata, a widely distributed plant in India, is one of nature's many plants
with medicinal characteristics. The potential medicinal property of Loranthus has been
reported in Ayurveda. It is reported to have diuretic, wound healing, anti-microbial,
anti-helminthic,
anti-fertility,
antioxidant,
anti-cancer,
anti-diabetic,
anti-
hyperlipidemic and anti-hypersensitive activities. Medicinal properties of mistletoes
are host specific. The antioxidant property of these parasitic plants might be due to their
phenolic compounds including tannins and flavonoids. However, it will be very
interesting to identify the novel antioxidant principles in the context of specific host
associations.
The present study was envisaged with a major aim of characterisation and
elucidation of bioactive antioxidants from D. falcata leaves by invitro assays and
identification of bioactive compounds through GC-MS/MS with prospective
pharmaceutical applications, and standardization of efficient and non-regenerative
method to control Loranthus.The experiments were carried out in Department of Plant Physiology, College of
Agriculture, Vellanikkara, Thrissur. In the first experiment the leaf samples of
Dendrophthoe falcata inhabiting different hosts namely mango, jackfruit, cocoa and
sapota were collected, powdered and extracted in various organic solvents such as
chloroform, petroleum ether, ethyl acetate, methanol and water followed by
computation of extract yields. Aqueous extracts of D. falcata inhabiting all the hosts
showed significantly higher (10.2 to 14.8%) yields compared to other solvents. Extract
yield in case of petroleum ether and ethyl acetate were reported to be lowest (1.6 to
2.9% respectively) compared to other solvents indicating polar inorganic extraction to
be advantageous, although novel and unique bioactive compounds could be effectively
extracted in the latter. D(Sapota) showed lowest extract yield in petroleum ether (1.6%)
and ethyl acetate (1.7%), whereas D(Jack) and D(Cocoa) had higher extract yields of
14.8% and 14.4% in water respectively. Free radical inhibition activity of D. falcata
were assessed using DPPH radical scavenging assay in different hosts across various
solvent extractions at different time intervals. Chloroform and water extracts of D.
falcata showed an increasing trend in inhibition activity with time. However, ethyl
acetate extracts marked a reduction in inhibition activity after two hours of incubation.
Qualitative phytochemical screening of different extracts of D. falcata on the four hosts
namely mango, jackfruit, cocoa and sapota were carried out to detect the presence of
alkaloids, phenols, saponins, flavonoids, terpenes, tannins and steroids. There was a
differential display of possession of different classes of phytochemicals by D. falcata
across different host associations which varied with the nature of solvent used for
extracting the antioxidant fractions. Chloroform extract of all the four hosts infested
with D. falcata contained alkaloids, phenols, flavonoids, terpenes and steroids. Ethyl
acetate extract had comparatively lesser phytochemicals, whereas methanolic extract
had alkaloids, saponins, phenols, flavonoids, terpenes and steroids. Water extract
yielded tannins along with other phytochemicals. Based on the antioxidant potential of
the different extracts and host specificities, eight samples were shortlisted for GC-
MS/MS analysis. Bioactive substances were detected in different extracts of D. falcata
during GC-MS/MS analysis. Two common and abundant bioactive principles viz. cis-
vaccenic acid and n-hexadecanoic acid were extracted in higher abundance in the
petroleum ether extracts of D(sapota) and D(jack) for the former and D(jack) for thelatter. Petroleum ether extraction resulted in the best profiling for both the bioactive
compounds from D(jack), indicating the association of D. falcata with jack as the most
potential one to be tapped for pharmacological uses.
The second experiment was carried out at Cocoa farm of Cocoa Research
Centre, Kerala Agricultural University, Thrissur where the cocoa trees infested with
Loranthus were tested for efficient management by impregnating the super absorbent
polymer, super absorbent cotton and super absorbent paper with a combination of Ethrel
and surfactants like oraganosilicone (OS)/alcohol ethoxylate (AE) @ 25mL/L of Ethrel
+ 0.5 mL/ L OS/AE and developed as a tape. Fresh and 1 week dried tapes were
comparatively assessed, of which fresh application performed better than dried. The
rate of defoliation also increased with time and after a while the number of leaves
defoliated remained constant. Among the applicant material used, super absorbent
polymer was found to be superior to super absorbent cotton and paper. Percent
defoliation due to both surfactants revealed that AE performed better than OS. Ethrel
along with surfactant alcohol ethoxylate (AE) as a sticky tape using superabsorbent
polymer as the impregnating material can be used as an effective management strategy
as AE is more eco-friendly than organosilicone. The tape method can also be an
alternative to spraying even in the event its longer time for defoliation, provided if it
ensures similar regrowth restriction efficiencies.