Medicinal plants serve as a universal remedy for several ailments because of the potent secondary metabolites such as alkaloids, polyphenolic compounds, terpenes, carotenoids etc. These metabolites help plants to cope up with the adverse effect of oxidative stress generated through environmental variables (Suyal et al. 2019a). Phenolic compounds, tannins, flavonols and flavonoids of Himalayan medicinal herbs has been identified for their antioxidant (Giri et al. 2017), anti-inflammatory and anti-cancer activity (Singh and Patra 2018) etc. Therefore, in present study we have investigated total phenolics, tannin, flavonoid, anti-oxidant and anti-mutagenic activity of P.cirrhifolium which might be responsible for its medicinal properties. A significant variation was observed in total phenols (1.89-3.47 mg GAE/g), tannins (1.41-2.50 mg TAE/g), flavonols (1.30-4.05 mg QE/g) and flavonoids (0.71-4.59 mg QE/g). Antioxidant property of rhizomes derived methanolic extract of P.cirrhifolium as evaluated by ABTS (3.26-5.12 mM AAE/100 g dw), DPPH (1.09-1.70 mM AAE/100 g dw) and FRAP (0.58-2.33 mM AAE/100 g dw) showed significant variation. These findings were in the agreement of Rawat et al. (2013) who reported tannins (2.24 mg TAE/g) and flavonoids (3.05 mg QE/g) in root extract of Habenaria edgeworthii. Similarly Giri et al. (2017) reported similar range of phenol, tannin, flavonol and antioxidant property in Astavarga species including P.cirrhifolium (2.41 mg/g flavonoid; 3.11 mg/g tannins; 1.85 mg/g flavonol; 4.42 mM AAE/100 g dw ABTS; 1.19 mM AAE/100 g dw FRAP). Likewise, similar range of total tannin (2.34 mg CE/g dw) and FRAP activity (0.27-1.78 mM AAE/100 g dw) was reported in Polygonatum verticillatum (Patra and Singh, 2018; Suyal et al., 2019).
The antioxidant property of flavonoid from diverse natural resources in the prevention of cellular DNA from damage through inhibition of ROS is documented (Azqueta and Collins 2016). Inhibition of DNA damage is evaluation to detect UV tolerance as a defense arrangement of high-altitude medicinal plants (Suyal et al. 2019a). Ultra violet radiation produces hydroxyl (OH) radical by peroxidizing H2O2, which can damage the plasmid DNA especially the supercoiled form.
Methanolic extract of diverse rhizome part of P.cirrhifolium in different population were studied for DNA prevention activity. The rhizome extract of different population showed significant (p<0.05) DNA recovery percentage which is ranged from 67.33- 84.95%. Therefore, extract of P.cirrhifolium and other high value medicinal plants could either check or dawdle the process of DNA damage and thus contribute to eliminate main disorders linked to DNA. Reports at the functionality of few Himalayan herbs to inhibit oxidative pressure due to DNA harm are available (Jugran et al. 2016; Giri et al. 2017; Suyal et al. 2019a). Information pertaining to genetic diversity in P.cirrhifolium is currently lacking. However, reports are available on genetic diversity studies in other species of genus Polygonatum (Kramp et al. 2009; Chung et al. 2014; Meng et al. 2014; Feng et al. 2020). Recently genetic variations of Polygonatum verticillatum populations were evaluated using ISSR markers (Suyal et al. 2021). P. cirrhifolium has been categorized as an endangered species in entire Himalayan region due to its limited population size coupled with poor regeneration (Suyal et al. 2019b), continuous harvesting, habitat degradation and grazing in the study area.
However, low variation atb genetic level is expected as a general reported trend in endangered plants with smaller population size (Manners et al. 2013). In present study, higher genetic diversity is reported in P.cirrhifolium using RAPD (He=0.339; Pp=92.12%) and ISSR (He=0.320; Pp=95.24%) markers. Likewise, many other threatened and endemic plant species despite of their small population size and restricted distribution, comprises high genetic diversity. For instance, Suyal et al. (2021) reported high (He=0.32; Pp%=85.49%) genetic variations in P. verticillatum using ISSR marker. Similarly, Naik et al. (2010) reported higher level (He=0.34; Pp%=92.37) of genetic variations in endangered Podophyllum hexandrum using RAPD marker; Tabin et al. (2016) in Rheum webbianum (He=0.34; Pp%=87%) using ISSR markers; Chaudhery et al. (2012) in Hedychium spicatum (RAPD- He=0.44; Pp= 89.58%). The higher genetic diversity in P.cirrhifolium might be due to its population distribution in different geographical conditions. In different geographical conditions the plant species may differ in their content due to diverse environmental variables (altitude, temperature, rainfall, humidity, etc.) and breeding system of the species (Zhang et al. 2020). Understanding the genetic variations inside and among populations is critical for basis of powerful and efficient conservation practices for rare species.
Most of the phenotypic variations, in P.cirrhifolium allotted inside population [RAPD- 78%; ISSR- 73%]. These results of within population variations are in line with reported variation for some endangered orchids and other threatened herbs e.g., Dendrobium officinale [RAPD- 78.88%; ISSR- 78.84%]; Fritillaria tubiformis subsp. moggridgei [RAPD-82.91%], Habenaria edgeworthii [ISSR- 74%] respectively [Ding et al. 2009; Mucciarelli et al. 2014; Giri et al. 2016]. The higher intra population variability of P. cirrhifolium can be elucidated based on its life history traits, particularly due to its breeding system. Breeding system of a plant species was found to influence the distribution of cistrontic diversity in plant populations. Additionally, factors like habitat disintegration, gene flow, and tiny population size additionally reported to contribute to the present difference (Nybom 2004).
The constant of genetic discrimination (GST) and gene flow (Nm) are two important parameters by which the genetic structure of population are often measured. Low genetic discrimination was recorded using RAPD and ISSR markers in P.cirrhifolium [RAPD: GST= 0.168; ISSR: GST= 0.221] although it was comparable to the average coefficients i.e. GST = 0.22 reported for out-crossing species (Nybom 2004) and GST=0.231for monocots (Hamrick and Godt 1990). Similar low genetic differentiation as reported elsewhere (Naik et al. 2010; Tiwari et al. 2015).
Factors like geographical isolation, small population size of target species, habitat fragmentation and genetic drift could be responsible for low genetic differentiation (Tiwari et al. 2015; Suyal et al. 2019b). A relatively high correlation between chemotypic and genetic markers were identified. Giri et al. 2016, observed similar results in H. edgeworthi, where ISSR marker revealed a noteworthy correlation with total phenolics [t=3.196; p<0.09]; Jugran et al. (2016) in Valeriana jatamansi [ABTS with (DPPH, r=0.482; p<0.05; FRAP, r=0.637; p<0.01)]; and Suyal et al. (2019a) in P. verticillatum [ABTS (DPPH, r=0.544; p<0.05)].