Anti-Viral Activity of Indian Plants

Abstract

Plants continue to be a major source for new chemical entities to develop novel therapeutic agents. Large number of plants has been shown to be active in vitro against a variety of human pathogenic viruses or their near congeners. In several cases the active compounds have been isolated and characterized. Very few of them, however, have been investigated in detail in vivo or taken to the clinic. Pure compounds like andrographolide, curcumin and glycyrrhizic acid as well as extracts of Azadirachta indica have shown activity against several viruses and should be investigated further for their therapeutic potential. An analysis of available data from several hundred species indicates that antiviral activity is more likely to be found in plants belonging to certain families. It is necessary to screen more plants of these families which are available in India to obtain further leads.

Introduction

Natural products have been, and continue to be, a major source of new chemical entities (NCE) for development of better therapeutic agents against infective and non-infective disorders. The bio-molecules are more stable, clinically more specific and available from renewable source [1]. Plants of Indian origin have provided several novel leads in the past [2] and are likely to yield more NCE in future also.

The contribution of natural products to anti-viral chemotherapy, however, has been more modest. Several factors have contributed to this scenario. Viral infections like the common cold are self limited and require only symptomatic treatment. Public health measures like vector control have succeeded in controlling vector transmitted infections. Similarly, development of effective vaccines has played a major role in eliminating diseases like small pox, near eradication of poliomyelitis and treatment of rabies. A major reason for limited input from Indian plants has been the non-availability of strict containment facility needed for such work at most institutions in the country. A large number of plants found in India have, therefore been investigated and found active in Japan, South Korea, US, etc. Data on all such plants also has been included in the present review along with analysis of data generated within the country. Plants active in viruses closely related to human virus [e.g. feline Human Immunodeficiency Virus (HIV) or duck hepatitis] have also been included. Maximum plants have been screened against Ranikhet disease (RNA) virus (RDV) and vaccinia (DNA virus) followed by herpes, HIV and hepatitis. The data in following sections has been arranged in the same order.

Most of the studies have used in vitro test systems and crude extracts of various parts of the plants. Pure compounds have been tested in some cases and in vivo procedures have been used in very few cases. In limited number of cases clinical studies also have been done. In several cases the name of the plant or family has been changed now. The name given in the original publication has been retained in the present review to avoid confusion but the names of family have been revised.

Ranikhet Disease and Vaccinia Viruses

CSIR Central Drug Research Institute Lucknow (CDRI) has been the pioneer institute to undertake large scale screening of Indian plants for anti-microbial and other biological activities using about 80 in vitro and in vivo tests. The program has used 50% ethanolic extracts of botanically authenticated plant samples. The extracts have been screened in vitro against one RNA virus (Ranikhet disease virus) and one DNA virus (vaccinia virus). Some samples have also been screened against encephalomyocarditis (EMCV), Japanese Encephalitis B (JE) and Semiliki Forest (SFV) viruses. Extracts showing high degree of activity were fractionated according to a standardized protocol to localize activity in one or more fractions. The results of testing 3,789 samples from 3,482 plants belonging to 233 families have been reported in a series of publications [3–14]. In addition, 967 of these plants were also tested for interferon-like activity against RD and vaccinia viruses [15]. A mid-term review of the work has also been published [16]. Antiviral activity was observed in 242 samples belonging to 96 families. The results have been summarized in Table 1. The plants have been listed under the appropriate families which have been arranged alphabetically. It also indicates plants where activity has been confirmed further in fractions or those exhibiting anticancer activity also.

Table 1.

Plants showing anti-viral activity in CDRI’s biological screening program

No.	Family & plant	Part	Activity	References
	Acanthaceae
1.	Adhatoda vasica	Rt	R	[3]
2.	Barleria cuspidata	Pl	R, r	[7, 15]
3.	Niligirianthus ciliatus	Pxa	V	[12]
4.	Strobilanthus wightianus	Px	R, r	[7, 15]
	Anacardiaceae
5.	Cotinus coggygria	Px	R	[3]
6.	Pistacia integerrima	Sb	R	[3]
7.	Rhus parviflora	Px	V, v, C	[5, 15]
8.	Rhus succedanea	Lf	R, r	[3, 15]
9.	Rhus succedanea	Px	R	[12]
	Annonaceae
10.	Miliusa macrocarpa	Px	R	[12]
	Apiaceae
11.	Pimpinella diversifolia	Pl	R	[3]
	Apocynaceae
12.	Ichnocarpus frutescens	Pl	R	[3]
	Aquifoliaceae
13.	Ilex wightiana	Pxa	V	[12]
	Araliaceae
14.	Hedera colchica	Px	R	[5]
15.	Schefflera rostrata	Lf, In	R	[12]
16.	Schefflera wallichiana	St	R	[12]
	Asclepiadeaceae
17.	Hemidesmus indicus	Pl	R, r	[3, 15]
	Aspidiaceae
18.	Polystichum biaristatum	Pla	R	[12]
	Asteraceae
19.	Artemesia parviflora	Pl	V	[6]
20.	Cnicus walichii	Pl	R	[3]
21.	Conyza visicidula	Pl	V,	[5]
22.	Eclipta alba	Pl	R	[3]
23.	Lagascea molis	Pl	r, V	[6, 15]
24.	Laggera pierodanta	Pl	R	[5]
25.	Saussurea obvallata	Fl	R	[11]
26.	Siegesbeckia orientalis	Pl	R, r	[3, 15]
27.	Senecio tenuifolius	Pl	R, r, v, C	[8, 15]
28.	Tagetes erecta	Pl	R	[4]
29.	Tagetes minuta	Pl	R, r	[4, 15]
30.	Vernonia cineria	Pl	R	[3]
31.	Vittadinia australis	Pl	V	[4]
	Berberidaceae
32.	Berberis lyceum	Rt	R	[3]
	Betulaceae
33.	Alnus nepalensis	Px	R	[12]
34.	Alnus nitida	Sb	R, V	[6]
	Bignoniaceae
35.	Heterophragma adenophyllum	Px	V	[5]
36.	Stereospermum suaveolens	Rt	R, r, C	[3, 15]
	Bixaceae
37.	Bixa orellana	Fra	V	[12]
	Bombacaceae
38.	Salmalia malabarica	Fl	R, r	[3, 15]
	Brassicaceae
39.	Descurainia sophia	Pl	R	[10]
	Caesalpiniaceae
40.	Caesalpinia bonducella	Rt	V	[3]
41.	Cassia auriculata	Pxa	R, r	[3, 15]
42.	Cassia auriculata	Rt	V, v	[3, 15]
43.	Cassia fistula	Sba	R, r, v, C	[3, 15]
44.	Cassia fistula	Pda	R, V	[3]
45.	Cassia tora	Pl	R	[3]
46.	Caesalpinia sepiaria	Rt	R,V	[4]
47.	Hardwickia binata	Pl	R, r, v	[5, 15]
48.	Tamarindus indica	Fl	R	[3]
	Capparaceae
49.	Capparis multiflora	Px	R	[12]
50.	Capparis longispina	Px	R	[3]
	Caprifoliaceae
51.	Lonicera leschenaultii	Px	R	[11]
	Celastraceae
52.	Euonymus angulatus	Pxa	R	[13]
53.	Salacia roxburghii	Px	R, r	[6, 15]
	Combretaceae
54.	Terminalia chebula	Fr	R	[3]
55.	Terminalia chebula	Lf	R	[11]
56.	Terminalia chebula	Sw	R, r	[11, 15]
57.	Terminalia paniculata	Pxa	R, C	[12]
	Connaraceae
58.	Connarus wighti	Px	R	[6]
	Convolvulaceae
59.	Cuscuta reflexa	Px	R, r	[4, 15]
	Cucurbitaceae
60.	Cucumis callosus	Px	R,V	[12]
	Cupressaceae
61.	Cupressus torulosa	Px	R,	[7]
	Cyperaceae
62.	Carex obscura	Pl	R	[10]
63.	Cyperus niveus	Pl	R, r	[3, 15]
64.	Cyperus pangorei	Pla	V	[12]
	Dilleniaceae
65.	Dillenia pentagyna	Sba	R	[14]
	Dipterocarpaceae
66.	Shorea robusta	Pxa	R	[10]
	Ebenaceae
67.	Diospyros chloroxylon	Px	R	[6]
68.	Diospyros marmorata	Pxa	R	[13]
69.	Diospyros peregrina	Sb	R, r	[3, 15]
70.	Maba nigrescens	Px	R, r, V, v	[6, 15]
	Elaeagnaceae
71.	Hippophae salicifolia	Sba	R	[11]
	Elaeocarpaceae
72.	Elaeocarpus tectorius	Lfa	R, V	[11]
73.	Elaeocarpus glandulosus	Px	R, C	[12]
	Ericaceae
74.	Agapetes odonalocera	Tua	R	[12]
75.	Rhododendron arboreum	Pxa	R	[14]
	Euphorbiaceae
76.	Aporosa villosula	Px	R	[13]
77.	Baccaurea ramiflora	Fr	S	[14]
78.	Bridelia retusa	Sba	R, r, C	[5, 15]
79.	Bridelia squamosa	Px	R	[6]
80.	Euphorbia prolifera	Pl	R, C	[3]
81.	Euphorbia royleana	St	R	[3]
82.	Glochidion hohenackerii	Px	R	[3]
83.	Glochidion subsessile	Px	R	[12]
84.	Glochidion zeylanicum	Pxa	R	[12]
85.	Jatropha glandulifera	Px	R, r	[10, 15]
86.	Kirganelia reticulata	Px	R	[3]
87.	Kirganelia tanarius	Px	R,V	[12]
88.	Mallotus resinosus	Px	R,V	[12]
89.	Margaritaria indica	Px	V	[12]
90.	Ricinus communis	Lf	V	[3]
91.	Emblica officinalis	Fr	R	[3]
	Fabaceae
92.	Crotolaria semperflorens	Px	R	[11]
93.	Dunbaria ferruginea	Pxa	R	[12]
94.	Indigofera pulchella	Rt	V	[3]
95.	Indigofera cassioides	Pxa	R	[12]
96.	Mundulea sericeae	Px	R, r	[6, 15]
97.	Ougeinia oojeinensis	Sb	R	[3]
98.	Phaseolus trilobus	Pl	V	[5]
99.	Sesbania procumbens	Px	R	[14]
100.	Sesbania sesban	Px	R	[6]
101.	Sophora glauca	Px	R	[7]
102.	Uraria lagopoides	Pl	R, r	[4, 15]
103.	Wisteria chinensis	Px	R	[12]
	Fagaceae
104.	Castanea sativa	Sb	R	[3]
105.	Castanopsis indica	Sb	R, r, C	[7, 15]
106.	Fagus sylvatica	Px	r, V	[5, 15]
107.	Lithocarpus dealbatus	Sb	R	[11]
108.	Lithocarpus dealbatus	Fr	R	[11]
109.	Lithocarpus dealbatus	Lf, Tw	R	[11]
110.	Quercus himalayana	Px	V	[11]
111.	Quercus lamellosa	Sb	R, r, V, v	[3, 15]
112.	Quercus lanceafolia	Sb	R, r, V, v	[3, 15]
113.	Quercus lineata	Sb	R	[3]
114.	Quercus pachyphylla	Sb	R	[3]
115.	Quercus thomsonii	Pxa	R	[12]
	Gentianaceae
116.	Canscora diffusa	Pl	R	[4]
	Guttiferae
117.	Garcinia talbotii	Pl	r, V	[5, 15]
	Hippocrateaceae
118.	Loeseneriella arnottiana	Pxa	R	[13]
	Juglandaceae
119.	Juglans regia	Lf	V	[6]
	Lamiaceae
120.	Leonurus sibiricus	Pl	V	[5]
121.	Leucas prostrata	Pla	V	[12]
122.	Rabdosia coetsa	Px	R	[11]
123.	Teucrium quadrifarium	Pl	r, V	[6, 15]
124.	Teucrium royleanum	Pl	R	[10]
	Lauraceae
125.	Cinnamomum iners	Px	R, r	[6, 15]
126.	Lindera pulcherrima	Px	R	[9]
127.	Litsea coriacea	Px	R	[13]
128.	Machilus gamblei	Lf	R	[3]
	Liliaceae
129.	Scilla hyacinthiana	Bu	S	[14]
	Loranthaceae
130.	Dendrophthoe falcata	Px	R, r	[4, 15]
131.	Dendrophthoe falcata	Px	V	[5]
132.	Helixanthera wallichiana	Pxa	R, V	[13]
	Lythraceae
133.	Lagerstroemia speciosa	Px	R	[4]
134.	Wodfordia fruticosa	Pl	R	[3]
	Malvaceae
135.	Thespesia populnea	Fr	R, r, C	[3, 15]
	Melastomataceae
136.	Melastoma normale	Pl	r, V	[4, 15]
137.	Memecylon umbellatum	Lf	R, C	[3]
	Meliaceae
138.	Aglaia anamallayana	Pxa	R	[13]
139.	Amoora wallichi	St	R, r, V, v	[3, 15]
140.	Melia azaderach	Sb	R, r	[4, 15]
	Menispermaceae
141.	Cocculus pendulus	Px	R, C	[4]
142.	Tinospora cardifolia	St	R	[3]
	Mimosaceae
143.	Abarema ungulata	Px	R	[13]
144.	Acacia auriculiformis	Px, Sb	r, v	[15]
145.	Acacia catechu	St	R	[3]
146.	Acacia raddiana	Px	R	[11]
147.	Albizzia procera	Px	r, V, C	[5, 15]
148.	Mimosa pudica	Pl	r, V	[4, 15]
	Moraceae
149.	Ficus hirta	Pxa	V	[12]
150.	Ficus religiosa	Sb	R, r	[3, 15]
	Moringaceae
151.	Moringa oleifera	Fr	V	[3]
	Myricaceae
152.	Myrica nagi	Sb	R	[3]
	Myristicaceae
153.	Knema linifolia	Sb	R	[14]
	Myrsinaceae
154.	Maesa chisea	Px	R	[7]
155.	Maesa indica	Px	V, v	[4, 15]
	Myrtaceae
156.	Eugenia codyensis	Pxa	R	[12]
157.	Eugenia mangifolia	Px	R	[11]
158.	Eugenia thwaitesii	Pxa	R	[12]
159.	Syzygium densiflorum	Px	R	[11]
160.	Syzygium kurzii	Pxa	S	[14]
161.	Syzygium occidentalis	Px	R	[12]
162.	Syzygium samarangense	Px	R,V	[12]
163.	Syzygium tetragonum	Px	R	[11]
	Ochnaceae
164.	Ochna integerrima	Px	R	[14]
	Oleaceae
165.	Olea polygama	Px	r, v	[17]
166.	Nyctanthes arbor-tristis	Fr	E	[14]
167.	Ximenia americana	Px	R	[6]
	Onagraceae
168.	Jussiaea suffruticosa	Pl	R, r, C	[7, 15]
169.	Ludwiga perensis	Pl	R, r	[4, 15]
	Orchidaceae
170.	Vanda spathulata	Pl	R, r	[7, 15]
	Papavaraceae
171.	Argemone mexicana	Pl	R	[3]
	Passifloraceae
172.	Passiflora mollissima	Px	R	[11]
	Pinaceae
173.	Cryptomeria japonica	Px	V	[4]
	Pittosporaceae
174.	Pittosporum tetraspermum	Px	R	[12]
	Plumbaginaceae
175.	Vogelia indica	Pl	R	[4]
	Poaceae
176.	Cynodon dactylon	Pxa	V	[3]
177.	Hordeum vulgare	Sd	R, r	[3, 15]
178.	Imperata cylindrica	Px	R, r	[5, 15]
179.	Isachne kunthiana	Pl	R	[12]
180.	Saccharum species	Lf	R	[11]
	Polygonaceae
181.	Polygonum glabrum	Px	R, r	[4, 15]
	Polypodiaceae
182.	Adiantum caudatum	Pl	R	[3]
183.	Asplenium nidus	Px	R, V	[12]
184.	Pseudodrynaria coronans	Rha	R	[12]
	Primulaceae
185.	Anagallis arvensis	Pl	R, r	[5, 15]
	Proteaceae
186.	Hakea saligna	Px	R	[7]
	Ranunculaceae
187.	Clematis buchanana	Px	V	[4]
188.	Clematis gouriyana	Px	R	[3]
	Rhamnaceae
189.	Scutia myrtima	Px	R, V	[3]
190.	Zizyphus glaberrima	Px	R, r	[6, 15]
191.	Zizyphus rugosa	Pxa	R	[13]
	Rosaceae
192.	Cotoneaster bacillaris	Px	R, r, V, v	[6, 15]
193.	Photinia integrifolia	Px	r, V	[5, 15]
194.	Prunus cornuta	Px	R, r	[6, 15]
195.	Rosa leschenaultii	Px	R	[11]
196.	Rubus hexagonus	Px	R	[11]
	Rubiaceae
197.	Cinchona ledgeriana	Lf	V, v	[6, 15]
198.	Gardenia jasminoides	Px	R, r	[4, 15]
199.	Gardenia turgida	Fr	R, C	[3]
200.	Ixora arborea	Px	r, V	[5, 15]
201.	Ixora nigricans	Px	R	[5]
202.	Psychotria truncata	Px	R, r,	[6, 15]
203.	Randia dumetorum	Sb	R	[3]
204.	Uncaria pilosa	Px	R	[12]
	Rutaceae
205.	Atalantia racemosa	Px	R, r	[5, 15]
206.	Evodia lunu-ankenda	Sb	R, r,	[7, 15]
207.	Paramignya monophylla	Px	R, C	[12]
	Sabiaceae
208.	Meliosma simplicifolia	Px	R	[11]
	Salicaceae
209.	Salix alba	Sb	R	[6]
210.	Salix babylonica	Pl	r, V	[4, 15]
	Samydaceae
211.	Casearia tomentosa	Px	R	[4]
	Santalaceae
212.	Osyris arborea	Lf	R	[3]
	Sapindaceae
213.	Allophylus serratus	Px	R, r	[6, 15]
	Sarauiaceae
214.	Saurauia roxburghii	Px	R	[7]
	Saxifragaceae
215.	Bergenia ligulata	Rh	R	[11]
	Scrophulariaceae
216.	Celsia coromandeliana	Pl	V, C	[4]
217.	Limnophila racemosa	Pl	V	[4]
	Solanaceae
218.	Atropa belladonna	Lf	R, r	[3, 15]
219.	Nicotiana plumbaginifolia	Pl	R, r, C	[4, 15]
220.	Solanum xanthocarpum	Pl	R, r, C	[3, 15]
221.	Withania somnifera	Pl	R, V	[3]
	Staphyleaceae
222.	Turpinea pomifera	Sba	J	[14]
	Sterculiaceae
223.	Byttneria grandifolia	Pxa	R	[14]
	Symplocaceae
224.	Symplocos paniculata	Lf	R, r	[3, 15]
	Theaceae
225.	Camellia japonica	Pxa	R	[12]
	Thymelaeaceae
226.	Lasiosiphon eriocephalus	St	R	[3]
	Tiliaceae
227.	Erinocarpus nimmonii	Lf	R, v	[11, 15]
228.	Grewia hirsuta	Px	R	[5]
229.	Grewia latifolia	Px	R, r	[4, 15]
230.	Tilia europaea	Px	R, r, C	[5, 15]
	Ulmaceae
231.	Ulmus wallichiana	Sb	R, r	[6, 15]
	Urticaceae
232.	Urtica dioica	Pl	R,	[10]
	Verbenaceae
233.	Gmelina arborea	Sb	R	[3]
234.	Vitex diversifolia	Px	R	[12]
	Vitaceae
235.	Cayratia auriculata	Fr	R	[12]
236.	Lea indica	Lf	R, r	[3, 15]
237.	Lea macrophylla	Px	V	[10]
	Zingiberaceae
238.	Cautleya spicata	Rt, Rh	R	[3]
239.	Costus speciosus	Pl	R, r, V, v	[6, 15]
240.	Zingiber capitatum	Pl	r, v	[15]
241.	Zingiber zerumbet	Rh	R	[11]
	Zygophyllaceae
242.	Fagonia critica	Px	R	[3]

Part used: Bu bulb, Fl flower, Fr fruit, Lf leaf, In inflorescence, Pd pod, Pl plant, Px plant without root, Rh rhizome, Rt root, Sb stem bark, St stem, Sw stem wood, Tu tuber, Tw twig

Activity: E encephalomyocarditis virus, J Japanese B encephalitis virus, R Ranikhet disease virus, r interferon induction, S semliki forest virus, V vaccinia virus, v interferon induction, C anticancer

^aActivity confirmed in fractions

Some of the active plants have been followed up at CDRI for isolation and characterization of the active constituents. The antiviral activity of (+) odorinol isolated from Aglaia roxburghiana has been reported by Joshi et al. [17]. Subsequently two new triterpinoids also have been isolated and characterized [18]. Lupeol has been identified as the active moiety of hexane fraction of Vicoa indica. It was effective against EMCV, RDV and SFV. Lupeol isolated from same fraction was active against RDV only [19]. Furomolligin isolated from Rubia cardifolia was active against EMCV [20].

The interferon like activity of five plants (Acacia auriculiformis, Cassia fistula, Olex polyama, Senecio tenuifolius and Zingiber capitatum) has been investigated further. The classical fractionation failed to localize activity in a particular fraction. The activity could be localized in each case in non-dialyzable fraction. It was destroyed on treating the fraction with trypsin. These results suggest the presence of an interferon-like or interferon inducing substance in the non-dialyzable fraction [15].

CDRI has also tested plants used as hepato-protective agents in traditional systems of Indian medicine for their anti-hepatitis B virus surface antigen (HB_sAg) activity in serum of patients or carriers. Promising results were obtained with Phyllanthus amarus [21] and Picrorhiza kurroa [22–26]. These have been reviewed in the section on hepatitis virus.

Herpes Virus

Activity against herpes virus has been reported in 49 Indian plants. These have been listed in Table 2. The activity is distributed widely and the plants belong to 34 families. Most of them have been reported active against herpes-1 virus though a few are active against both herpes-1 and 2. In 12 cases the strain used has not been mentioned. Only four publications have reported in vivo activity. Pure isolated compounds have been tested in 26 cases. Two of the compounds glycyrrhizin and lupeol are active against other human viruses also and this has been indicated at appropriate places in this review. Unfortunately none of them appear to have been followed up further. The results have been published in 43 papers and only 9 of them are from Indian laboratories. Table 2 includes only those plants from foreign publications which are found in India.

Table 2.

Indian plants active against herpes simplex viruses in vitro

Plant	Family	Product	Strain	References
1. Adansonia digitata	Bombaceae	Ext	HSV	[27]
2. Aglai odorata	Meliaceae	Ext	1a	[28]
3. Aloe vera	Liliaceae	Ext	2	[29]
4. Andrographis paniculata	Acanthaceae	Diterpenes	1	[30]
5. Atlantia sp.	Rutaceae	Pyrophorbide	2	[31]
6. Azadirachta indica	Meliaceae	Ext	1	[32]
7. Barleria lupulina	Acanthaceae	Iridoid glycoside	1	[33]
8. Bauhinia racemosa	Caesalpiniaceae	Ext	HSV	[34]
9. Bauhinia variegate		Ext	1,2	[35]
10. Bidens pilosa	Asteraceae	Ext	1,2	[36]
11. Cedrus libani	Pinaceae	Ext, oil	1	[37]
12. Cissus quadrangularis	Vitaceae	Ext	1,2	[38]
13. Conyza aegyptica	Asteraceae	Ext	HSV	[27]
14. Cyperus rotundus	Cyperaceae	Ext	1	[39]
15. Euphorbia peplus	Euphorbiaceae	Diterpene esters	2	[40]
16. Glycyrrhiza glabra	Fabaceae	Glycyrrhizin	HSV	[41]
17. Heliotropium marifolium	Boraginaceae	Alkaloid	HSV	[42]
18. Holoptelea integrifolia	Ulmaceae	Ext	HSV	[43]
19. Houttuynia cordata	Sarauiaceae	Ext	1,2	[36]
		Pure compounds	1	[44]
20. Hypericum hookerianum	Hyperaceae	Ext	1	[45]
21. Hypericum mysorense		Ext	1	[45]
22. Lippia alba	Verbenaceae	Ext	1	[46]
23. Melia azaderach	Meliaceae	Ext	2a	[47]
		Meliacine	1	[48]
24. Mentha piperata	Lamiaceae	Essential oil	1,2	[49]
25. Momordia charantia	Cucurbitaceae	Ext	1	[50]
26. Moringa oleifera	Moringaceae	Ext	1a	[28]
27. Myrica rubra	Myricaceae	Pure compounds	2	[51]
28. Neerium indicum	Apocynaceae	Ext	HSV	[43]
29. Pandanus amaryllifolius	Pandanaceae	Pandanin	1	[52]
30. Peganum harmala	Rutaceae	Ext	1	[53]
31. Phyllanthus emblica	Euphorbiaceae	Pure compounds	HSV	[54]
32. Phyllanthus urinaria		Pure compounds	1,2	[55]
33. Pinus massoniana	Pinaceae	Ext	HSV	[56]
34. Plantago major	Plantaginaceae	Ext	HSV	[56]
35. Portulaca oleracea	Portulacaceae	Polysaccharides	2	[57]
36. Salvia officinalis	Lamiaceae	Ext	1,2	[58]
37. Santalum album	Santalaceae	Oil	1,2	[59]
38. Scinaia hatei	Liagonaceae	Polysaccharides	HSV	[60]
39. Scoparia dulcis	Scrophulariaceae	Scopadulcic acid	1	[61]
40. Solanum torvum	Solanaceae	Torvanol A	1	[62]
		Torvoside H	1
41. Sorghum bicolor	Poaceae	Peptide	1	[63]
42. Strobilanthus cusia	Acanthaceae	Lupeol	1	[64]
43. Swertia chirata	Gentinaceae	Ext	1	[65]
44. Syzygium aromaticum	Myrtaceae	Eugenin	1	[66]
45. Syzygium jambos		Ext	1	[67]
46. Taracetium vulgare	Asteraceae	Ext, Parthenolide	1,2	[68]
47. Usnea complanta	Usneaceae	Ext	1	[45]
48. Ventilago denticulate	Rhamnaceae	Ext	1a	[28]
49. Withania somnifera	Solanaceae	Ext	1	[69]

Ext crude extracts in different solvents; HSV unspecified strain, 1 or 2 HSV-1 or HSV-2

^aTested in vivo

Human Immunodeficiency Virus

Large number of papers has been published in recent years reporting anti-HIV activity in numerous natural products, partly because of the large screening program of US National Cancer Institute. Activity has been reported only in 38 Indian plants in 32 papers. These have been shown in Table 3 and belong to 28 families. Data on 41 materials has been reported and 24 of them are pure compounds. Most investigators (26) have studied the activity on HIV-1 and in 10 cases the strain has not been mentioned. HIV-2 has been included in two studies only. Two of the reported plants have been found active against feline immunodeficiency virus (FIV), a close congener of HIV. Most of the publications in this case also are from foreign laboratories and there are only seven Indian publications. There have been claims of usefulness of Ayurvedic and Siddha formulations in treatment of AIDS but no reliable clinical data is available either with these formulations or with the plants listed in Table 3. Data with Curcuma longa has not been included in this table because curcumin isolated from this plant and its several semi-synthetic and synthetic analogues have been tested. The data has been included in concluding remarks.

Table 3.

Indian plants with in vitro anti-HIV activity

Plant	Family	Product	Strain	References
1. Acacia nilotica	Mimosaceae	Ext	HIV	[70]
2. Acacia tortilis		Ext	1	[71]
3. Ailanthus allisima	Simaroubaceae	Ocotillone	1	[72]
4. Alpinia galanga	Zingiberaceae	Ext	1	[73]
5. Anisomeles indica	Lamiaceae	Ovatodiolide	HIV	[74]
6. Artemesia caruifolia	Asteraceae	Coumaryl spermines	1	[75]
7. Camellia japonica	Theaceae	Camelliatannin H	1	[76]
8. Cardiospermum helicabum	Sapindaceae	Ext	1,2	[77]
9. Chrysanthemum morifolium	Asteraceae	Flavonoids	1	[78]
10. Cinnamomum cassia	Lauraceae	Ext	1,2	[77]
11. Desmos sp.	Annonaceae	Flavonoids	HIV	[79]
12. Ficus glomerata	Moraceae	Ext	1	[80]
13. Glycyrrhiza glabra	Fabaceae	Glycyrrhizin	1	[41]
14. Harrisonia perforate	Simaroubaceae	Ext	1	[80]
15. Hyssopus officinalis	Lamiaceae	Ext	1	[81]
16. Illicium verum	Illiaceae	Illicinone-A	HIV	[82]
17. Justicia replans	Acanthaceae	Ext	HIV	[83]
18. Lippia javanica	Verbenaceae	Piperitenone	1	[84]
19. Mimusops elengli	Sapotaceae	Mimusopic acid	HIV	[85]
20. Momordia charantia	Cucurbitaceae	Lectin	1	[86]
		Protein MRK 29	1	[87]
21. Morinda citrifolia	Rubiaceae	Ext	1	[88]
22. Nelumbo nucifera	Nymphaceae	Cocalaurine	HIV	[89]
		Nuciferine	HIV
23. Pedilanthus sp.	Euphorbiaceae	Pedilotanin	1	[90]
24. Pericampylus glaucus	Menispermaceae	Periglaucines	1	[91]
25. Phaseolus vulgaris	Fabaceae	Lectin	1	[86]
26. Polyalthea suberosa	Annonaceae	Furans	HIV	[92]
27. Polygonum viscosum	Polygonaceae	Quercitin	1	[93]
28. Ricinus communis	Euphorbiaceae	Lectins	1	[86]
29. Rhus sinensis	Anacardiaceae	Benzofuranones	1	[94]
		Rhuscholide A	HIV	[95]
30. Sambucus nigra	Caprifoliaceae	Ext	HIV(f)	[96]
31. Schisandra rubriflora	Schisandraceae	Rubrifloxine	1	[97]
32. Scoparia dulcis	Scrophulariaceae	Ext	1	[98]
33. Sida sp.	Malvaceae	Ext	HIV	[99]
34. Sophora flavescens	Fabaceae	Ext	1	[76]
35. Terminalia chebula	Combretaceae	Galloyl glucose	1	[100]
36. Urtica dioica	Urticaceae	Ext	FIV	[96]
37. Ximenia americana	Oleaceae	Ext	1	[101]
38. Zingiber officinale	Zingiberaceae	Ext	1	[73]

Ext crude extract in different solvents; HIV strain not specified; 1, 2 HIV I or II strain; FIV feline immunodeficiency virus (has many common features with HIV) [96]

Hepatitis Viruses

Large number of medicinal plants has been used for treatment of hepatic disorders in most traditional system of medicine. The parameters generally followed were clearance of jaundice and return of liver function tests to normalcy. Clearance of viraemia in infective hepatitis, the commonest hepatic disorder, became an important parameter after the demonstration of carrier stage and possible induction of malignancy in such persons. One of the earliest demonstrations of viral clearance was provided by the pioneering studies of Thyagarajan et al. [106] with Phyllanthus amarus. This led to screening of large number of plants for activity against the virus. The availability of the duck model for in vivo studies materially facilitated these studies. Protective effect has been reported with 17 Indian plants belonging to 14 families. These have been listed in Table 4. Most of the plants have been tested against hepatitis B virus by several in vitro procedures. The active compound has been isolated and characterised in nine of these plants.

Table 4.

Indian plants active against hepatitis virus in vitro

Plant	Family	Product	Strain	References
1. Agrimonia eupatoria	Rosaceae	Ext	B	[102]
2. Alpinea galanga	Zingiberaceae	Ext	C	[73]
3. Bupleurum sp.	Apiaceae	Saikosaponins	B	[103]
4. Glycyrrhiza glabra	Fabaceae	Glycyrrhizin	B, Ca	[41]
5. Hypericum perforatum	Hypericaceae	Hypericin	Ca	[104]
6. Oenanthe javanica	Apiaceae	Phenolics	B	[105]
7. Pericampylus glaucus	Menispermaceae	Periglaucines	B	[91]
8. Phyllanthus amarus	Euphorbiaceae	Ext	Ba	[21,106]
9. Phyllanthus urinaria		Ext	Ba	[107]
10. Picrorhiza kurroa	Scrophulariaceae	Picroliv	B	[22]
11. Potentila anserine	Rosaceae	Triterpine saponins	B, E	[108]
12. Ranunculus scleratus	Ranunculaceae	Apigenins	B	[109]
13. Rubia cardifolia	Rubiaceae	Naphthoquinones	B	[110]
14. Saussurea lappa	Asteraceae	Ext	B	[111]
15. Terminalia chebula	Combretaceae	Ext	B	[112]
16. Wrightia tinctoria	Apocynaceae	Ext	C	[113]
17. Zingiber officinale	Zingiberaceae	Ext	C	[73]

Ext crude extract in different solvents; B, C, E the strain of virus used

^aClinical study

Several hepatoprotective plants have been tested for anti-hepatitis B virus surface antigen (HB_sAg) activity in vitro using serum from patients or asymptomatic carriers harbouring the infection. Neutralizing activity has been reported with extract of Phyllanthus amarus [21]. A purified standardized extract (Picroliv) and a pure compound catalpol isolated from Picrorhiza kurroa were also found active while andrographolide (active constituent of Andrographis paniculata) and silymarin were inactive [22].

Clinical studies have been undertaken with some of the active plants in patients of infective hepatitis. As already reported above [23] efficacy of Picroliv has been demonstrated in Phase III multicentric trials. Beneficial effects have been reported with Phyllanthus amarus and glycyrrhizin also. These and other studies have been reviewed by Handa in a comprehensive publication [114] on hepatoprotective activity of Indian medicinal plants.

Respiratory Viruses

Interest in respiratory virus has increased following the recent epidemics of SARS and H₁N₁ infection. Activity has been reported in 18 Indian plants belonging to 16 families. Pure compounds isolated from plants have been tested in nine cases. Activity has been reported against five respiratory viruses. Activity against influenza has been observed in seven samples and against H₁N₁ in four cases. One sample was active against SARS. The data about active plants has been summarized in Table 5.

Table 5.

Indian plants active in vitro against respiratory viruses

Plant	Family	Product	Virus	References
1. Alpinia officinarium	Zingiberaceae	Diaryl heptanoids	H1N1	[115]
2. Andrographis paniculata	Acanthaceae	Andrographolide	Influenza	[116]a
			H1N1
3. Avicennia marina	Avecenniaceae	Ext	Newcastle	[117]
4. Barleria prionitis	Acanthaceae	Iridoids	Resp. Syn.b	[118]
5. Berginia ligulata	Saxifragaceae	Ext	Influenza	[43]
6. Caesalpinea sappan	Cesalpineaceae	Sappan chalcones	Influenza	[119]
7. Curcuma longa	Zingiberaceae	Curcumin	Newcastle	[120]
8. Ephedra sinica	Ephedraceae	Catechinc	H1N1	[121]
9. Gardenia sp.	Rubiaceae	Ext	Influenza	[122]d
10. Glycyrrhiza glabra	Fabaceae	Glycyrrhizin	Influenza	[41]
			Resp. Syn.
			SARS
11. Hottuynia cordata	Piperaceae	Ext	SARS	[123]
12. Neerium indicum	Apocynaceae	Ext	Influenza	[43]
13. Nigelia sativa	Ranunculaceae	Ext	Newcastle	[117]
14. Pandanus amaryllifoius	Pandanaceae	Pandanin	H1N1	[52]
15. Phyllanthus amarus	Euphorbiaceae	Ext	Newcastle	[120]
16. Punica granatum	Puniaceae	Ext	Influenza	[124]
17. Wickstroemia indica	Thymelaceae	Daphnoretin	Resp. Syn.	[125]
18. Zizyphus spira-christi	Rhamnaceae	Ext	Newcastle	[117]

Ext crude extract in different solvents

^aTested in vivo

^bRespiratory synticial virus

^cMain source of catechin is Acacia catechu [126]

^dTested in vitro and in vivo

Pox Viruses

Interest in this group of viruses has continued because of continued occurrence of chicken-pox and measles infection. Only 14 plants have been reported active against a variety of pox viruses. These plants belong to 13 families. Glycyrrhizin from Glycyrrhiza glabra is the only pure compound reported active. Extract from Hibiscus sabdariffa is the only product showing activity against measles. Most of the extracts have been found active against fowl pox. Details of activity have been shown in Table 6.

Table 6.

Indian plants active in vitro against pox viruses

Plant	Family	Product	Virus	References
1. Acacia nilotica	Fabaceae	Ext	Fowl pox	[117]
2. Aristolochia bracteolate	Aristolocheaceae	Ext	Fowl pox	[117]
3. Avicenna marina	Avecennaceae	Ext	Fowl pox	[117]
4. Azadirachta indica	Meliaceae	Ext	Buffalo pox	[127]
			Fowl pox	[128]
			Measles
			Vaccinia
5. Bauhinia variegata	Ceasalpineaceae	Ext	Vaccinia	[35]
6. Cissus quadrangularis	Vitaceae	Ext	Fowl pox	[117]
7. Eugenia jambolana	Myrtaceae	Ext	Buffalo pox	[129]
8. Glycyrrhiza glabra	Fabaceae	Glycyrrhizin	Vaccinia	[41]
			Varicella	[130]
9. Hibiscus sabdariffa	Malvaceae	Ext	Measles	[131]
10. Ipomea carnea	Convolvulaceae	Ext	Fowl pox	[117]
11. Maerua oblongifolia	Capparidaceae	Ext	Fowl pox	[117]
12. Ocimum sanctum	Lamiaceae	Ext	Vaccinia	[3]
13. Prosposis chilensis	Mimosaceae	Ext	Fowl pox	[117]
14. Trebulus terrestris	Zygophyllaceae	Ext	Fowl pox	[117]
15. Trigonella foenum graecum	Fabaceae	Ext	Fowl pox	[117]

Ext crude extract in different solvents

Other Viruses

Activity in several Indian plants has also been reported against a variety of other viruses causing human infection or their close congeners. Table 7 shows such plants belonging to 24 families. In 10 cases pure compounds isolated from plants have been found active. The list includes 12 viruses. The preparations showing activity against chikungunya, Japanese encephalitis and rotavirus are of particular interest due to wide occurrence of these infections in the country and need to be investigated on a priority basis.

Table 7.

Indian plants active in vitro against other human viruses

Plant	Family	Product	Virus	References
1. Adansonia digitata	Bombacaceae	Ext	Polio	[27]
			Sindbis
2. Aegle marmelos	Rutacaeae	Ext	Coxsackie	[132]
3. Alpinea galanga	Zingiberaceae	Ext	Cytomegalus	[73]
4. Artocarpus integrifolia	Moraceae	Ext	Rotavirus	[133]
5. Azadirachta indica	Meliaceae	Ext	Chikungunya	[128]
			Coxsackie	[134]
6. Baccaurea ramiflora	Euphorbiaceae	Ext	Semilikia	[14]
7. Bauhinia variegate	Caesalpineaceae	Ext	Ves Stomatitisb	[35]
8. Berberis aristata	Berberidaceae	Berberine	Friends Leuc	[25]
9. Camelia sinensis	Theaceae	Triterpinoids	Epstein Barr	[135]
10. Conyza aegyptica	Asteraceae	Ext	Polio	[27]
			Sindbis
11. Curcuma longa	Zingiberaceae	Curcumin	Epstein Barr	[136]
			Friends Leu	[25]
			HPVd	[136]
			Polio	[120]
12. Glycyrrhiza glabra	Fabaceae	Glycyrrhizin	JEe	[137]
			Polio	[138]
			Ves Stomatitis	[41]
13. Heliotropium marifolium	Boraginaceae	Alkaloids	Coxsackie	[42]
			Polio
14. Hernandia ovigera	Hernandiaceae	Lignans	Epstein Barr	[139]
15. Kalanchoe pinnata	Crassulaceae	Bryophyllin A	Epstein Barr	[140]
16. Lippa alba	Verbenaceae	Ext	Polio	[64]
17. Mallotus philippensis	Euphorbiaceae	Triterpinoids	Epstein Barr	[141]
18. Momordia charantia	Cucurbitaceae	Ext	Sindbis	[50]
19. Myristica fragrans	Myristicaceae	Ext	Rotavirus	[134]
20. Nyctanthes arbor-tristis	Oleaceae	Ext	EMCVf	[14]
21. Paedaria scandens	Rubiaceae	Paederoside	Epstein Barr	[26]
22. Phyllanthus amarus	Euphorbiaceae	Ext	Polio	[120]
23. Picrorhiza kurroa	Scrophulariaceae	Ext	Epstein Barr	[26]
		Picroliv	EMCV	[24]
			Friends Leuk	[25]
24. Plumbago zeylanica	Plumbaginaceae	Ext	Coxsackie	[46]
25. Scilla hyacinthine	Liliaceae	Ext	Semiliki	[14]
26. Spondias lutea	Anacardiaceae	Ext	Rotavirus	[132]
27. Syzigium jambos	Myrtaceae	Ext	Ves Stomatitis	[67]
28. Turpinea pomifera	Staphleaceae	Ext	JE	[14]
29. Zingiber officinale	Zingiberaceae	Ext	Cytomegalus	[73]

Ext crude extract in different solvents

^aSemiliki Forest virus

^bVesicular stomatitis

^cFriends leukemia

^dHuman papilloma virus

^eJapanese encephalitis

^fEncephalomyocarditis virus

Concluding Remarks

The broad based biological screening program of CDRI had included tests for several other activities also with the same standardized protocol. An analysis of the results has shown that each particular activity was preferentially observed in certain families. The top 11 families for anti-viral activity and three other major activities have been arranged in rank order in Table 8. It will be observed that rank order is different for different activities even though some families exhibit more than one type of activity. The top 11 families in each case contain 35–45% of the plants for the concerned activity. The 11 families identified for anti-viral activity contain about 41% of the 242 active plants from 96 families. About 27% plants reported active against other viruses and included in Tables 2, 3, 4, 5, 6 and 7 also belong to these 11 families. It should be useful to screen other plants of these families to obtain more active plants. It will be evident from data in Tables 1 and 8 that many plants and families have both anti-viral and anticancer properties. It may be mentioned also that several smaller countries like Egypt [39], Nepal [43], Sudan [54] and Togo [27] have undertaken systematic evaluation of their flora for anti-viral activity following the lead given by CDRI.

Table 8.

Top 11 families for selected pharmacological activities in CDRI plants

Anti-viral	Anti-cancer	CNS active	Hypoglycemic
No. of active plants
239	131	639	156
No. in top 11 families
98	58	228	61
% in top 11 families
41.0	44.2	35.7	39.1
Rank order of top 11 families
Euphorbiaceae	Asteraceae	Ericaceae	Cucurbitaceae
Fabaceae	Euphorbiaceae	Minosaceae	Fagaceae
Asteraceae	Fabaceae	Fabaceae	Zingiberaceae
Fagaceae	Combretaceae	Euphorbiaceae	Rutaceae
Myrtaceae	Lamiaceae	Rosaceae	Verbenaceae
Rubiaceae	Meliaceae	Lauraceae	Euphorbiaceae
Rosaceae	Anacardiaceae	Malvaceae	Fagaceae
Caesalpineaceae	Celastraceae	Rubiaceae	Acanthaceae
Lamiaceae	Convolvulaceae	Lamiaceae	Lamiaceae
Lauraceae	Acanthaceae	Asteraceae	Rubiaceae
Anacardiaceae	Rosaceae	Poaceae	Asteraceae

It is evident from the data reviewed above that little effort has been made to study the marine flora around the vast Indian coast line for antiviral compounds. Several Indian mangrove plants (Ceriops decandra, Excocaria agallocha and three species of Rhizophora i.e. lamarckii, mucoranata and spiculata) have been reported to exhibit potent anti-HIV activity [142] highlighting the need of further exploration of this valuable resource.

Most of the data reported in this review is from in vitro studies and the leads do not appear to have been followed up. This is partly because of lack of suitable animal models for several infections and partly due to lack of the requirement containment facility in majority of Indian institutions. It is suggested that multi-pronged strategy should be adopted to utilise these leads. There are certain viral infections like Japanese encephalitis, chikungunya or rotavirus which are major national concern. Only few leads are available against them and these need to be followed.

A number of pure compounds have demonstrated activity against several viral infections. These are compounds of varying chemical complexity ranging from simple compounds like curcumin to complicated structures like iridoids glycosides. Adequate attention has not been paid to use them as basic templates to optimise the activity in synthetic or semi-synthetic derivatives. Successful use of this strategy has been made in the case of andrographolide [143] and curcumin [136], for example.

Activity has also been reported in certain compounds which have undergone extensive clinical evaluation in non-viral diseases. Their available safety and dosage regimen data would help in initiating clinical evaluation in viral infection where in vitro or in vivo activity data is available. Andrographolide is a potent hepatoprotective agent [114] besides being active against herpes [30], influenza and H₁N₁ infections [116]. Dehydroandrographolide succinic acid monoester is active against HIV [143]. Another clinically authenticated hepatoprotective agent Picroliv [23] is also active against several viral infections including hepatitis B [24–26]. Curcumin has received the maximum attention after its activity against HIV was demonstrated. Large number of semi-synthetic or synthetic derivatives have been prepared and tested for anti-HIV activity. Its boron complexes; semi-synthetic reduced curcumin, allyl curcumin and tocopheryl-curcumin and synthetic analogues dicafferoyl methane and rosemarinic acid are highly active against HIV in a variety of in vitro protocols. Curcumin is active against herpes simplex 2 in a mouse model and Human papilloma and Epstein Barr viruses in vitro. These activities have been reviewed recently by Krishnaswamy [136]. Its in vitro activity against Friends leukaemia [25], Newcastle and Poliomyelitis viruses [120] has also been reported. Fiore et al. [41] in a recent review have provided reference for activity of glycyrrhizin and its analogues against herpes, hepatitis (including clinical trial), influenza, respiratory syncytial, SARS and vesicular stomatitis viruses. Other investigators have found it active against Japanese encephalitis [137], poliomyelitis [138], vaccinia and varicella [130]. It perhaps has the widest spectrum of antiviral activity among the natural products so far investigated. Adequate clinical evaluation is necessary to assess its role in treatment of viral disorders. Azadirachta indica also is a promising plant, even though most of the studies have used its extract. It has a variety of compounds and also has a long history of use in traditional medicine in many countries of the world. The viruses against which the extracts or some of the isolated compounds have shown activity include chikungunya, fowl pox, measles, vaccinia [128], buffalo pox [127], Coxsackie [134] and herpes [32]. Detailed studies against some of these viruses, specially herpes and chikungunya are strongly warranted. In conclusion it may be stated that the rich and valuable resource of Indian plants needs to be more extensively exploited to provide new drugs for the treatment of viral disorders.