Polygonum sachalinensis F. Schmidt ex Maxim (Nakai) (Polygonaceae)

8.3.1 Names, morphological characters and general invasive impacts

Synonyms: Reynoutria sachalinensis F.Schmidt ex Maxim; Fallopia sachalinensis F.Schmidt ex Maxim, Polygonum sachalinense F.Schmidt, Pleuropterus sachalinensis F.W.Schmidt ex Maxim, Tiniaria sachalinensis (F.W.Schmidt ex Maxim.) Janch [USDA 2009]

Common names:Giant knotweed, sacaline, Sakhalin knotweed

Morphological characters: Similar in appearance to P. cuspidatum (Japanese knotweed), the main difference is in its size, a somewhat variable characteristic. Leaf size and overall plant size are bigger. Its main morphological caracters and the differences with P. cuspidatum are listed in Table 2-10, Figure 2-7

General impacts as invasive species: Table 2-11

Figure 2-7 Photographs of Giant knotweed (Polygonum sachalinensis) invasive growth in Champex, Switzerland, taken by Dr. Andrew Marston, LPP, in May 2008.

Table 2-10 Morphological characters of P. sachalinensis and the main differences with P. cuspidatum [NWCB 2009]

Morphological characters ofP. sachalinensis

General Morphology An herbaceous perennial, strongly rhizomatous, growing over 12 feet tall Stems Hollow, jointed and swollen at the nodes, giving a bamboo-like appearance

Leaves

Petiolate, their arrangement is alternate, often exceed one foot long, and are 2/3 as wide – twice the size of P. cuspidatum

The leaf shape is strongly cordate (heart-shaped)

Inflorescence Sparse, with axillary panicles, smaller than P. cuspidatum

Flowers

Gynodioecious, with the inflorescence producing pistillate flowers and perfect flowers on separate plants, the size does not increase with maturity. For P. cuspidatum, the flowers are prominently winged, and their size increases significantly with age

Giant knotweed produces viable pollen, and hybridizes with Japanese knotweed. This hybrid is morphologically similar, and often confused with Japanese knotweed in the United Kingdom. This hybrid is the source of viable pollen in England, since Japanese knotweed does not produce fertile male plants in England. The hybrid has a very low fertility rate.

8.3.2. Previous chemical investigations

P. sachalinensis has not only a similar appearance to P. cuspidatum, but also similar secondary metabolites (Table 2-12, Figure 2-8). Anthraquinones, flavonoids and stilbenes are

present in both species. The systematic comparison of these two species was done in this study.

Table 2-11 Properties of P. sachalinensis as invasive species [NWCB 2009]

Properties of P. sachalinensis as invasive species

Origin The Sakhalin Islands of northern Japan, its name translates ‘from Sakhalin Island’

Introduction This garden ornamental escaped, and was commonly found in the north eastern United States by the 1950’s

General Impact

Found along stream banks, in moist waste places, neglected gardens, roadsides, and railroad right-of-ways, invasiveness, habitat choices, the impacts to riparian areas similar to P.

cuspidatum, and they both have extensive rhizomes which make established populations very difficult to control. Once established, giant knotweed also dominates and out-compets native or beneficial plants.

Table2-12: Isolated secondary metabolites from Polygonum sachalinensis

Classes Organs Compounds

Leaves Anthraquinones

Flowers

Emodin (9), physcion (10), emodin-8-O- β –glucoside (46), physcion-8-O-β-glucoside (49) [Kang and Woo 1982a, Umek and Bohinc 1983], emodin-1-O- β – glucoside (98), physcion-1-O-β-glucoside (99) [Inoue et al. 1992]

Leaves Flavonoids

Flowers

quercetin (100) [Nakaoki and Morita 1956],

quercetin-3-O- β –L-arabinofuranoside (avicularin, 101) [Kang 1981], quercetin 3- O- β –D –glucopyranoside (61),

quercetin 3-O- β –D-glucofuranoside (102) [Kang and Woo 1982b], quercetin-3-O- β –D-galactopyranoside (62),

quercetin-3-O- β –D-glucuronopyranoside (103) [Zhang et al. 2005]

Phenylpropanoid

glycosides Rhizomes vanicoside A (104) and B (105) [Kawai et al. 2006, Kumagai et al. 2005]

Roots Stilbenes

Rhizomes

Resveratrol (52), piceid (53) [Chi et al. 1983]

Anthocyanins Leaves Cyanidin (106), malvidin (107), and delphinidin [Kuznetsova 1979]

Phenolcarboxylic acids Aerial part Protocatechuic (79), vanillic, caffeic, p-hydroxybenzoic, ferulic, and salicylic acids [Vechar et al. 1980]

Others Aerial part myricyl alc, phytosterol, polysaccharides , free glucose, arabinose, and sorbose, free amino acids, β-tocopherol [Kim et al. 1979]

O

Figure 2-8 Examples of isolated secondary metabolites from P. sachalinensis

8.3.3. Previously reported bioactivities of P. sachalinensis

Antioxidant activity: Bioassay-guided fractionation of methanol extract of P. sachalinensis flower using DPPH assay has led to the isolation of three anthraquinones and three flavonoids.

All isolated compounds had remarkable antioxidant activities with free radical 1, 1-diphenyl-2-picrylhydrazyl (DPPH) scavenging, superoxide radical scavenging and Cu²⁺-mediated low density lipoprotein (LDL) oxidation assay [Zhang et al. 2005].

Glucosidase inhibitory activity: The phenylpropanoid glycosides, vanicoside A and B, isolated from rhizomes of giant knotweed showed β-glucosidase inhibitory activity, with IC50

values of 59.8 and 48.3 mg/mL (59.9 and 50.5 mM), respectively. In contrast, p-coumaric acid and ferulic acid, corresponding to phenylpropanoyl moieties of vanicosides, exhibited very little inhibition [Kawai et al. 2006].

Antimicrobial activity: The antimicrobial compounds against the fish pathogen Photobacterium damselae subsp. Piscicida were isolated from P. sachalinense rhizomes. The structures of two antimicrobial compounds were identified to be phenylpropanoid glycosides, vanicosides A and B, respectively. Their antimicrobial activities were modest, in contrast to higher activities of antibiotics, florphenicol, ampicillin and amoxicillin, which have been generally used for treating pasteurellosis. The activities of the vanicosides, however, were higher than those of ferulic acid and p-coumaric acid themselves. It was suggested that the structures of phenylpropanoids esterified with sucrose were essential for higher antimicrobial activity of vanicosides and also acetylation of sucrose might affect the activity against the bacterium [Kumagai et al. 2005].

Allelochemicals: The root exudates from P. sachalinense in a recirculating system significantly inhibited lettuce seedling growth. TLC agar plate bioassay showed the inhibitory activity corresponded to the two yellow pigment bands, which were isolated and identified as emodin and physcion. Both compounds exhibited inhibitory activities against the seedling growth of several testing plant species, while emodin-1-O-β-D-glucoside (98) and physcion-1-O-β-D-glucoside (99) showed no phytotoxic activity against lettuce seedlings. The rhizome with roots and fallen leaves contained emodin and physcion at relatively high concentrations.

Emodin also occurs in the soil of this plant community in the fall. Thus, these anthraquinones are responsible for the observed interference and are potent allelopathic substances [Inoue et al. 1992].

Other: Extracts from the leaves of the giant knotweed induced a systemic resistance against powdery mildew on cucumbers, tomatoes and several other plants. [Kowalewski and Herger 1992]