Validation of tribal claims on Dioscorea pentaphylla L. through phytochemical screening and evaluation of antibacterial activity

Plant Science Research, 35 (1&2): 49-55. 2013

Sanjeet Kumar et al., (2013)
^{sanjeet.biotech@gmail.com}

Department of Botany, Ravenshaw University, Cuttack-753 003, Odisha, India

ABSTRACT

The present study elucidates the ethnobotanical uses of various parts of Dioscorea pentaphylla L. as divulged from the structured interview and cross verification with rural and tribal communities of selected adjoining areas of Similipal Biosphere Reserve forest, Odisha. Further, it validates the tribal claims using phytochemical screening and antibacterial activity. Acetone, Methanol and aqueous extracts showed relevant zone of inhibition against two Gram positive bacteria Streptococcus mutans (MTCC *497) and Streptococcus pyogenes (MTCC 1926); three Gram-negative bacteria Vibrio cholera (MTCC 3906), Shigella flexneri (MTCC 1457) and Salmonella enterica typhi (MTCC 1252).

Kew Words: tribal claims, Dioscorea pentaphylla L., antibacterial activity, validation

1.     Introduction

Use of antibiotics during 20^th century has substantially reduced the threat of infectious diseases (Gould, 2008). Nevertheless, over the years, there has been a decrease in microbial susceptibility to existing antimicrobial agents responsible for critical point drug resistance in healthcare departments and in communities (Wise, 2011). In fact the theme of the World Health Day 2011 was “Antimicrobial resistance: no action today, no cure tomorrow” (Nash et al., 2011). It is a big problem in pharmaceutical industry and for future health care. Recently different researchers have reported the urgent need for new antimicrobial agents to replenish the arsenal of anti-infective agents or drugs.  It is reported that, on an average, two or three antibiotics are launched each year (Osbourn, 1996). After a downturn in that pace in recent decades, the pace is again quickening as scientists realize that the effective life span of any antibiotics is limited (Alper, 1998; Eisenberg et al., 1993; Moerman, 1996; Wise, 2011). Therefore it is necessary to know more about antimicrobial resistance (AMR), the mechanisms of action and screening of secondary metabolites from bio-wealth (Osman et al., 2012).  Plant materials are of wide use in traditional systems of medicine, and in several communities of the developing world (Fischbash and Walsh, 2009). They are the only resources available for the treatment of different microbial infections among many rural and tribal communities. Most of the common plants have been reported to have antimicrobial activity, still a number of unexplored wild plants are available in the forests having good ethnic values as traditional medicine (Dianella, 2012). There is need for the screening of bioactive compounds present in such plants and the antimicrobial activities of their extracts (Ginsburg and Deharo, 2011). Among those unexplored plants wealth, genus Dioscorea is very common, found abundant in wild forests of Odisha (Kumar and Satpathy, 2011b; Kumar et al., 2012a; Misra et al., 2013). There are 11 wild species of this genus found in Odisha (Kumar et al., 2012a). Among them, Dioscorea pentaphylla L. (Plate-1: A, B and C) is easily available (Kumar et al., 2012a; Sinha and Lakra, 2005). Tribal communities use its part as food and against microbial infections. Still, in modern era, the rural and tribal communities of around world have been using the plant extracts against microbial infections (Kumar et al., 2013). In Odisha, the Dongaria Kondha, a primitive tribe of Niyamgiri has been using plant parts of Cassia fistula against skin infections (Kumar et al., 2012b), The Hill-Kharia tribe, Mankirdia tribe, Santhal tribe, Ho tribe, Kolha tribe, Munda tribe and Bhumij tribe of Simlipal Biosphere Reserve have been using rhizome of Costus specious, Dioscorea bulbifera and Dioscorea pentaphylla against skin infections (Misra et al., 2013). All these evidences make a sound platform for the study on antibacterial activity of plant extracts.  In this study, Dioscorea pentaphylla L. is selected due to diverse medicinal values and rich availability in the state. It is also an unexplored wild tuber crop having sound food and economic values among the rural and tribal communities of Odisha. Therefore an attempt has been made to validate the tribal claims (ethnobotanical values) to evaluate the bioactive compounds present in plant extracts and their antibacterial activities against three Gram-positive bacteria and two Gram-negative bacteria.

1.     Results and discussion

Field survey revealed that Dioscorea pentaphylla L. is very popular as food and medicine among the tribal communities of SBR and its adjoining areas (Table 1). After repeated persuasions with rural and tribal communities, some sound / less known ethnobotanical values on Dioscorea pentaphylla L. was collected and documented (Table 1). Tubers are edible after much preparation. It is bitter in taste but after traditional preparation such as continuous washing overnight and boiling, tubers are consumed as vegetables (Table 1). Apart from use as food, tuber paste is also used against skin infections and other diseases (Table 1). Based on the tribal claims, further phytochemical screening and antibacterial activity was done for the validation (Table 2, 3 & 4).  The qualitative analysis of phytochemical screening has shown the medicinal potential of the plant. Terpenoids, Tannin, Saponin, Glycosides, Reducing sugar, Flavonoids and Phenolic componunds are major bioactive compounds present in the tuber, leaf and bulbils of Dioscorea pentaphylla L. (Table 2). Presence of these bioactive compounds in tuber, leaf and bulbils extracts are thought to be effective against different bacterial and fungal infections (Table 2 & 4). In order to establish the antimicrobial potency of the plant parts the antibacterial activities against known human pathogens were studied and the results are shown in Table 3 in detail. The zone of inhibition (cm) of standard antibiotic against used strains was also shown in Table 3. The antibacterial activity of acetone, methanol and aqueous extracts of tuber showed excellent zone of inhibition (cm) against Vibrio cholera (MTCC 3906), Shigella flexneri (MTCC 1457), Salmonella enteric typhi (MTCC 1252), Streptococcus pyogenes (MTCC 1926) and Streptococcus mutans (MTCC *497). Aqueous extract of tuber showed excellent activity against MTCC 1926 (Table-3; Fig-1 & 2). MTCC 1926 is responsible for skin infections (Hay et al., 1994). It has been observed that methanol and acetone extract found to be active against Gram-negative bacteria Vibrio cholera (MTCC 3906). Therefore it is

Table 1

Ethnobotanical values of Dioscorea pentaphylla L. among the tribal communities (adjoining areas of SBR)

Plant Part(s)	Collection site(s)	Races	Medicinal Use(s)	Mode of use(s)	Other use(s)
Tubers	Padampur	Santhal	Skin Infections	Macerated tuber paste is applied externally on lesions	Edible
	Jashipur haat	Mankardia	Cold	Approx 250 gm tuber is boiled with about 1 lit of water and juice is prepared. One cup of juice with salt is taken thrice a day to remove cough.	Edible
	Bisoi	Ho	Constipation	One year old tubers are left overnight in running water and this tubers are used as chips to cure stomach pain and constipation problems.	Edible
	Karanjia	Santhal	Poor appetite	After successive boiling, the tubers are eaten as vegetables and to reduce poor appetite twice a week.	Edible
	Haatibaadi	Santhal	Against cut	Approx 200 gm of fresh tuber is crushed with water and made into paste, which is used externally on cut and other similar wounds thrice a day till cure.	Edible
Leaves	Padampur	Munda	Against joint pain	Leaves paste made with Karanja oil (Pongamia pinnata) and  is rubbed on joint	.......

presumed that these compounds can be used for formulation of new drugs which may be effective against cholera and can also fight against antimicrobial resistance. The extracts also showed good growth inhibition against Gram-positive bacteria Streptococcus mutans (MTCC *497).

Table 2

Detection of bioactive compounds in plant parts of Dioscorea pentaphyla L.

Plant part(s)	Solvent used	Bioactive compound(s) detected
Tubers	n-Hexane	Terpenoids
	Acetone	Tannin, Flavonoids, Glycosides and Reducing sugar
	Methanol	Tannin, Phenolic compounds and Steroids
	Water	Saponin, Reducing sugar and Glycosides
Leaves	n-Hexane	No bioactive compounds detected
	Acetone	Tannin, Saponin, Flavonoids, Terpenoids, Glycosides and Reducing sugar
	Methanol	Tannin, Saponin, Phenolic compounds and Glycosides
	Water	Tannin, Saponin, Flavonoids, Reducing sugar and Phenolic compounds
Bulbils	n-Hexane	Terpenoids
	Acetone	Tannin, Flavonoids, Glycosides and Reducing sugar
	Methanol	Tannin, Phenolic compounds and Steroids
	Water	Saponin, Reducing sugar and Glycosides

The compounds  present in this extract might be playing active role against primary etiologic agents of coronal caries and root caries for oral diseases such as dental and periodontal caused by Streptococcus mutans (Hay et al., 1994), Streptococcus sobrinus (Ellen et al., 1985), Streptococcus oralis (Sansone et al., 1993) etc. The extracts also showed relevant results against Gram-negative bacteria Salmonella enterica typhi (MTCC 1252). 

Table 3

Antibacterial activity of Dioscorea pentaphylla tuber extracts with standard

(Data represents mean ± SD at three experiments each with three replicates)

Strain(s)	Zone of inhibition (cm)			Extract / Standard
	500 µg/ml	1000 µg/ml	2000 µg/ml	Methanol Extract
MTCC 3906	0.55 ± 0.07	1.05 ± 0.07	1.00 ± 0.14
MTCC 1252	0.85 ± 0.07	1.10 ± 0.00	1.45 ± 0.07
MTCC 1457	1.20 ± 0.14	1.35 ± 0.21	1.50 ± 0.14
MTCC 1926	1.00 ± 0.14	1.40 ± 0.21	1.50 ± 0.00
MTCC *497	0.85 ± 0.21	1.20 ± 0.41	1.40 ± 0.14
MTCC 3906	1.05 ± 0.07	1.27 ± 0.03	1.41 ± 0.01	Acetone Extract
MTCC 1252	0.95 ± 0.07	1.37 ± 0.03	1.72 ± 0.10
MTCC 1457	0.87 ± 0.03	1.19 ± 0.01	1.44 ± 0.07
MTCC 1926	0.92 ± 0.10	1.29 ± 0.01	1.77 ± 0.03
MTCC *497	0.92 ± 0.10	1.2 ± 0.14	1.49 ± 0.01
MTCC 3906	1.10 ± 0.14	1.10 ± 0.14	1.30 ± 0.14	Aqueous Extract
MTCC 1252	0.70 ± 0.14	0.85 ± 0.07	1.05 ± 0.07
MTCC 1457	1.10 ± 0.14	1.15 ± 0.21	1.45 ± 0.07
MTCC 1926	1.20 ± 0.14	1.50 ± 0.14	1.60 ± 0.14
MTCC *497	0.85 ± 0.21	1.20 ± 0.00`	1.47 ± 0.03
Strain(s)	Diameter of inhibition zones (cm)			Kanamycin
MTCC 3906	1.63 ± 1.53
MTCC 1252	1.56 ± 0.58
MTCC 1457	1.73 ± 0.58
MTCC 1926	1.76 ± 0.58
MTCC *497	1.73 ± 0.58

 (MTCC 3906: Vibrio cholera; MTCC 1252: Salmonella enteric typhi; MTCC 1457: Shigella flexneri; MTCC 1926: Streptococcus pyogenes; MTCC *497: Streptococcus mutans)

Salmonella enterica typhi is considered as deadly bacteria causing typhoid fever and being responsible for the dead of more than 6 lakh people annually all over the world (Falkaw et al., 2004). Strains were tested for their vulnerability using chloramphenicol, trimethoprim and amoxicillin and found all strains are resistance (Philippa et al., 1998) to all these formulation. The tuber extracts being effective against this fatal strain, can be used in new drug formulation against Salmonella enterica typhi (MTCC 1252).

Table 4

Correlation of Tribal Claims with bioactive compounds & antibacterial activity of Dioscorea pentaphylla L. tuber extracts for validation.

Plant Parts	Tribal claims	Correlation with bioactive compounds	Correlation with antibacterial activity	Supporting literature
Tubers	Aqueous paste is used against skin infections	Tannin presence in methanol extract and saponin presence of aqueous extract of Dioscorea pentaphylla L. tuber may be responsible for curing skin infections.	Antibacterial activity of aqueous extract against Streptococcus pyogenes were excellent that is 1.20, 1.50 and 1.60 diameter (zone of inhibition in cm) at 500 µg/ml, 1000 µg/ml and 2000 µg/ ml respectively.	Okwu and Okwu, (2004); Mohan and Kalidas,(2010); Aderotimi and Samuel, (2006)
		Correlation with bioactive compounds
	Cold	Presence of Terpenoids in n-Hexane extract might be responsible.		Musa et al., (2009)
	Cut and wounds	Presence of Flavonoids in acetone extract might be responsible.		Musa et al., (2009)
Leaves	Joint pain	Presence of Flavonoids in acetone and methanol extract might be responsible to reduce inflammation and pain.		Majumadar et al., (2008)
Bulbils	Not bitter in taste	No indication of Saponin in aqueous may be indicated less bitterness properties.		Magdolena, (2009)

1.     Conclusion

Dioscorea pentaphylla L. a wild tuber crop abundant in Similipal Biosphere Reserve forest and its adjoining areas possesses wide ethnobotanical values among the rural and tribal communities of the study areas. Presence of bioactive compounds has shown the potential antibacterial and pharmacological action of this wild tuber. Present study might be useful to supplement scientific information to establish tribal claims for the presence of phytocompounds and medicinal values. Further research is needed to document the detail bioactive compounds present in such wild plants predominant in Odisha and their probable use against known pathogens and antibiotic resistance as well.

Acknowledgement

The authors are grateful to the Field Director, Similipal Biosphere Reserve, HOD Department of Botany, Ravenshaw University for providing the facilities for this work. The authors wish to thank the traditional tribal healers of Similipal Biosphere Reserve and its adjoining areas and also thank to Dr. R.C. Misra, National Bureau of Plant Genetic Resource, Base Centre, Cuttack.