A Perspective on therapeutic potential of weeds

‘Horse Hoeing Husbandry’ named famous writing by Jethro Tull (1731) mentioned irst time the word ‘weed’ [1]. Weeds may be considered as plants whose abundance must be over or above a speci ic level can cause major environmental concern [2]. Aldrich and Kremer, 1997 de ined weed as a part of dynamic ecosystem [3]. Plant originated in natural environment and, in response to imposed or natural environments, evolved, and continues to do so, as an interfering associate with crops and activities. Weeds may interfere with the utilization of land and water resources thereby adversely affect human welfare [4]. According to Ancient Indian Literature earth is blessed with diverse lora and every existing plant has their own importance. Some plants are considered unwanted but they may have bene icial properties. Scholars are trying hard to explore the hidden potential of such unwanted plants [5]. Weeds have interactions with other organisms and some of these interactions can have direct effects on the functioning of agro-ecosystem [6]. They serve as an indirect resource for predatory species [7] and it could alternative food sources for organisms that play prominent role in insect control [8]. Weeds have a unique travel history. Clinton L. Evans in his Abstract


Introduction
'Horse Hoeing Husbandry' named famous writing by Jethro Tull (1731) mentioned irst time the word 'weed' [1]. Weeds may be considered as plants whose abundance must be over or above a speci ic level can cause major environmental concern [2]. Aldrich and Kremer, 1997 de ined weed as a part of dynamic ecosystem [3]. Plant originated in natural environment and, in response to imposed or natural environments, evolved, and continues to do so, as an interfering associate with crops and activities. Weeds may interfere with the utilization of land and water resources thereby adversely affect human welfare [4]. According to Ancient Indian Literature earth is blessed with diverse lora and every existing plant has their own importance. Some plants are considered unwanted but they may have bene icial properties. Scholars are trying hard to explore the hidden potential of such unwanted plants [5]. Weeds have interactions with other organisms and some of these interactions can have direct effects on the functioning of agro-ecosystem [6]. They serve as an indirect resource for predatory species [7] and it could alternative food sources for organisms that play prominent role in insect control [8].
Weeds have a unique travel history. Clinton L. Evans in his Abstract Nature gives us a diverse plethora of fl oral wealth. Weeds have been recognized as invasive plant by most of scholars in today's world with extraordinary travel history. They are considered to be noxious for adjoining plant species and also as economic hazard. Weeds inhabited in almost entire biomes and have capability to survive in harsh conditions of environment thereby become source of inspiration for fi nding novel phytoconstituents. Weeds play a signifi cant role in absorbing harmful micro pollutants that are aff ecting ecosystem adversely. There are so many examples like canna lily, bladder wort, coltsfoot, giant buttercup etc. playing crucial part in sustaining environment. Diff erent isolation and characterization approaches like high pressure liquid chromatography, gas chromatography, ion exchange chromatography, nuclear magnetic resonance, mass spectroscopy etc. have also been fetched for obtaining novel constituents from weeds. The main aim of this review is to analyze the therapeutic potential of weeds established in New Zealand and eff ort to unfold the wide scope of its applications in biological sciences. Upon exploration of various authorized databases available it has been found that weeds not only are the reservoir of complex phytoconstituents exhibiting diverse array of pharmacological activities but also provide potential role in environment phytoremediation. Phytoconstituents reported in weeds have immense potential as a drug targets for diff erent pathological conditions. This review focuses on the literature of therapeutic potential of weeds established in New Zealand and tried to unveil the hidden side of these unwanted plants called weeds.

Therapeutic potential of weeds established in New Zealand
Weeds have been explored for diverse pharmacological actions like anti cancer, anti microbial, anti-in lammatory, antioxidant, antiviral etc. as mentioned in table 3 and igure 1.

Anti-in lammatory weeds:
A study by Akhtar, et al. 2019 investigated the anti-in lammatory properties of Hedera helix and its major compounds on Staphylococcus aureus induced in lammation in mice. Hederacoside-C isolated from weed exerted profound anti-in lammatory effects [72]. Mexican water lily (Nymphaea mexicana) was found to be potent COX-2 inhibitor [75]. Active compounds isolated from aerial parts of weed Clematis vitalba when evaluated in vivo against carrageenan, serotonin, PGE-2 induced hind paw edema showed antinociceptive and antipyretic effects [78]. Methanolic extract of leaves of Tecomaria capensis signi icantly prevented increase in volume of paw edema [55]. Extract of Persicaria hydropiper exerted marked anti-in lammatory effects [106]. Aqueous extract alongwith compounds (calceorioside B, homoplantaginin, plantamajoside) isolated from the aerial parts of Plantago major showed inhibition against hyaluronidase enzyme [89].  Weeds acting on CNS: Methanolic extract of stem bark of darwin's barberry (Berberis darwinii) inhibited acetylcholinestrase in vitro with IC 50 value of 1.23±0.05 microg/ mL thereby provide relief in alzheimer's disease [60]. Alkaloid solanocapsine isolated from weed Solanum pseudocapsicum reported to inhibit activity of enzyme acetylcholinestrase [73]. Nettle (Urtica urens) exhibited anxiolytic activity in mice when evaluated using hole board test, light-dark box test and rota rod test. Extract showed increased head-dip duration and head-dip counts in hole board test [98]. Aqueous (50-400 mg/ kg i.p.) and methanolic extracts (100-400 mg/kg i.p.) of Pig's ear (Cotyledon orbiculata) exhibited anticonvulsant activity which predominantly delayed onset of seizures induced by N-methyl-dl-aspartic, bicuculline, picrotoxin in mice models [79].
Other pharmacological activities of weeds: Aqueous extract of Akebia quinata showed positive effect against fatigue in mice exposed to chronic restraint stress when evaluated using forced swimming behavioral test, sucrose preference and open ield tests [57]. n-butanol fraction of weed Equisetum hyemale exerted antiprotozoal effects against Trypanosoma evansi trypomastigotes after nine hours exposure [81].  reported osteogenic activities of Humulus lupulus in MC3T3-E1 cell lines [69]. Ethanolic extract of weed Galium aparine stimulated the transformational activity of immunocompetent blood cells in vitro [91]. Aqueous extract of aerial parts of Mentha pulegium (20 mg/kg) showed antihyperglycemic effect by marked improvement in oral glucose tolerance test in streptozotocin induced diabetic rats [99]. Butanolic extracts of aerial parts of Lamium album and Lamium pupureum showed haemostatic activity in wistar rats when evaluated by tail bleeding time determination and acenocoumarol carrageenan test compared to vitamin K [100]. Anagallis arvensis (Scarlet pimpernel) leaf extract showed molluscicidal activity against Biomphalaria alexandrina at LC 50 37.9 mg/l and LC 90 48.3 mg/l [101]. Hexane extract rich in lupeol acetate of weed scotch thistle (Cirsium vulgare) prevented carbon tetrachloride induced liver damage in rats by diminishing lipid peroxidation and nitric oxide levels [102]. Extracts of Sonchus oleraceus (Sow thistle) were reported to be nephroprotective against kidney ischemia reperfusion injury in wistar rats [105]. Water extract, ethanol extract, hexane/acetone extract obtained from Achillea millefolium (Yarrow) were effective against Babesia canis parasite at 2 mg/ml concentration [107].

Conclusion
Humans de ine weeds as per their appropriateness and understanding of the plant. A plant investigated as weed in some region may be a plant of medicinal importance for another region. The usefulness of weeds has been ignored by humans for long time because of their invasive growth, competitors of genuine crop and no economic value. This human behaviour might be developed over time due to lack of proper knowledge of phytochemical screening as well as therapeutic potential of weeds. Weeds are the sources of human food, fodder in agriculture, shelter for some animals, helpful against soil erosion, indicators of soil nutrients, as well as sources of commercially important essential oils. In this era weeds have been extensively explored for their immense phytopharmacological prospects. It is evidenced that weeds have been sources of potential targets for different pathological conditions. However there is need of more scienti ic and clinical investigations required in assessment of toxicity pro ile to get the maximum potential of weeds. Weeds have protective role in environment as a component of phytoremediation and for sustainable ecosystem. Because of immense therapeutic potential implicit by weeds a new chain of thoughts emerge in our mind to consider the value of these important plants so called 'weeds'. Are they need to be rede ined or we need to rethink the concept of weeds? It is clear from the studies documented in this review that the approach of whether a plant is wanted or not should depends on its pharmacological potential and role in ecosystem other than merely the competitive effect of plant with the particular crop. Further advancements are required in order to spin the concept of weeds into therapeutic weeds.