Contribution of militarine and dactylorhin A to the plant growth‐inhibitory activity of a weed‐suppressing orchid, Bletilla striata

Abstract

The methanol extract of Bletilla striata, an ornamental orchid in eastern Asia, exhibited plant growth-inhibitory activity. It was purified by continuous chromatography, based on the inhibitory activity against the growth of lettuce seedlings, resulting in two glycosidic compounds, militarine and dactylorhin A.The EC50 values of militarine and dactylorhin A against the radicle elongation of the lettuce seedlings were 0.28 and 0.88 mmol L -1 , respectively.The amount of militarine and dactylorhin A in the methanol extract of the aerial part of B. striata was calculated to be 5.6 and 7.5 mg g -1 fresh weight, respectively. The inhibitory activity of militarine and its content in the methanol extract revealed that the plant growth-inhibitory activity of the extract of B. striata was mainly related to militarine. The inhibitory activity of militarine against the growth of Italian ryegrass and timothy were of the same level as that of lettuce.

Advances in militarine: Pharmacology, synthesis, molecular regulation and regulatory mechanisms

“…It appears the potential to inhibit plant growth and can served as a green source to improve crop productivity. In this study, it also revealed that dactylorhin A of Militarine structural analogue (- O -β-D-Glu (dactylorhin A) but not –OH (Militarine), which is linked in the C2 position of Militarine chemical structure) did not display any effect in inhibiting plant growth [ 2 ] ( Table 1 ). Further analyses have shed that Militarine regulates the growth of Italian ryegrass and timothy with inhibitory concentration almost equivalent to Lettuce [ 2 ].…”

“…Modern-day pharmacological studies confirmed that Militarine does not only act as an important inhibitor that suppresses the growth of plant [ 2 ], but also occupies important position within therapeutic management for various diseases. Studies by researchers have highlighted the significance of Militarine in pharmacology.…”

“… Pharmacological effects Pathological models Active substance Material structure characteristics Source of material plants Study design Regulatory mechanisms Molecular targets/mechanisms Reference Plant inhibitors The growth of the host plant of Militarine is inhibited by surrounding weeds (environmental stress) Militarine The structural analogue of Militarine, Dactylorhin A (- O connected at the C2 position of Militarine)-β-D-Glu) does not exhibit plant inhibitory activity Methanol extract of fresh B. striata and aboveground components In vivo Inhibiting the elongation of Lettuce embryonic roots and axes are achieved with EC50 values of 0.28 mmol L −1 and 1.03 mmol L −1 As an allelochemical, Militarine inhibits the growth of weeds in its surroundings. [ 2 ] Protection of lung SiO 2 thickens the alveolar septa and induces inflammatory infiltration, thereby inducing the Bax/Bcl-2 pathways Gymnoside II (the main active substance) and Militarine account for 1.31 ± 0.05 % and 12.12 ± 0.05 % of the ethanol extracts, respectively Militarine stably binds to antioxidant HO-1 protein through its own hydrogen bonding N-butanol extract from B. striata (40 mg/kg) In vivo and in vitro Inhibition of SiO 2 induced apoptosis and ROS production in alveolar epithelial cells through Nrf2 pathway dependent mechanisms Nrf↑, HO-1↑, γ-GCSc↑, ROS↓, Bax↓, Bcl-2↑, cleaved-caspase 3↓, Bax/Bcl-2↓ [ 24 ] SiO 2 has cytotoxicity and induces pneumonia, pulmonary fibrosis, and lung cancer by acting on alveolar epithelial cells 25 μmol/L Militarine processes 25 μg/cm 2 SiO 2 Gymnoside II is an ester hydrolysis product and synthetic raw material of Militarine Alcohol extract from B. striata In vivo It significantly reduced SiO 2 induced lung inflammation and oxidative stress in mice ROS↓, Nrf↑, Nrf downstream gene HO-1, and γ-GCSc↑ [ ...…”

“…Its hallmark feature lies in the 2-isobutylmatic acid of the chemical structures of O-glycosides and absorption maximum is shifted nearly 223 nm [ 1 ]. Not only hold its properties in plant growth bio-inhibition been defined [ 2 ], but it also possesses a rich pharmacological activities and serves as an invaluable source of pharmaceuticals that include the treatment of lung injuries [ 3 ], improvement in cognitive impairment [ 4 ], neuroprotection [ 5 ] and antioxidant capacity [ 6 ], among others. Militarine is proposed to be composed of saccharides and non-saccharide fractions (aglycone), materialized by condensation of hydroxyl groups in C2 epitopes of two molecules of glucose and phenolic hydroxyl in aglycone.…”

Isolation of microsatellite markers for Bletilla striata and cross-amplification in other related species

“…Those species are also commonly used as a horticultural subject covering both indoors and out cultivation in North American and European areas (Pridgeon, 2005). Recently, B. striata has been reported to be able to suppress various weed species (Sakuno et al, 2010). As the traditional herb medicine using more than 1500 years, pseudobulbs of Bletilla have been widely used in Eastern Asian countries to treat alimentary canal mucosal damage, ulcer, bleeding, bruises and burns.…”