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New Inhibitors of the DENV-NS5 RdRp from Carpolepis laurifolia as Potential Antiviral Drugs for Dengue Treatment

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Since a few decades the dengue virus became a major public health concern and no treatment is available yet. In order to propose potential antidengue compounds for chemotherapy we focused on DENV RNA polymerase (DENV-NS5 RdRp) which is specific and essential for the virus replication. Carpolepis laurifolia belongs to the Myrtaceae and is used as febrifuge in traditional kanak medicine. Leaf extract of this plant has been identified as a hit against the DENV-NS5 RdRp. Here we present a bioguided fractionation of the leaf extract of C. laurifolia which is also the first phytochemical evaluation of this plant. Five flavonoids, namely quercetin (1), 6-methylapigenin-7-methylether (2), avicularin (3), quercitrin (4) and hyperoside (5), together with betulinic acid (6), were isolated from the leaf extract of C. laurifolia. All isolated compounds were tested individually against the DENV-NS5 RdRp and compared with four other commercial flavonoids: isoquercitrin (7), spiraeoside (8), quercetin-3,4’-di-O-glucoside (9) and rutin (10). Compounds 3, 4, 6, 8 and 10 displayed IC50 ranging from 1.7 to 2.1 μM, and were the most active against the DENV-NS5 RdRp.
The article was published by Academy of Chemistry of Globe Publications © Published 05/01/2014 EISSN:
Rec. Nat. Prod. 8:3 (2014) 286-289
New Inhibitors of the DENV-NS5 RdRp from Carpolepis laurifolia
as Potential Antiviral Drugs for Dengue Treatment
Paul Coulerie
, Alexandre Maciuk
, Cécilia Eydoux
, Edouard Hnawia
Nicolas Lebouvier
, Bruno Figadère
, Jean-Claude Guillemot
Mohammed Nour
Laboratoire Insulaire du Vivant et de l’Environnement, Université de la Nouvelle-Calédonie, BP R4,
98851 Nouméa Cedex, Nouvelle-Calédonie
Laboratoire BioCIS, UMR CNRS 8076 Université Paris-Sud XI, 5 rue J.-B. Clément, 92296
Châtenay-Malabry, France
Laboratoire AFMB, UMR 6098, Université Aix-Marseille, Campus de Luminy, 13288
Marseille cedex 09, France
(Received May 31, 2013; Revised November 6, 2013; Accepted December 14, 2013)
Abstract: Since a few decades the dengue virus became a major public health concern and no treatment is
available yet. In order to propose potential antidengue compounds for chemotherapy we focused on DENV RNA
polymerase (DENV-NS5 RdRp) which is specific and essential for the virus replication. Carpolepis laurifolia
belongs to the Myrtaceae and is used as febrifuge in traditional kanak medicine. Leaf extract of this plant has
been identified as a hit against the DENV-NS5 RdRp. Here we present a bioguided fractionation of the leaf
extract of C. laurifolia which is also the first phytochemical evaluation of this plant. Five flavonoids, namely
quercetin (1), 6-methylapigenin-7-methylether (2), avicularin (3), quercitrin (4) and hyperoside (5), together with
betulinic acid (6), were isolated from the leaf extract of C. laurifolia. All isolated compounds were tested
individually against the DENV-NS5 RdRp and compared with four other commercial flavonoids: isoquercitrin
(7), spiraeoside (8), quercetin-3,4’-di-O-glucoside (9) and rutin (10). Compounds 3, 4, 6, 8 and 10 displayed IC
ranging from 1.7 to 2.1 µM, and were the most active against the DENV-NS5 RdRp.
Keywords: Myrtaceae; Carpolepis laurifolia; Dengue Virus; Flavonoids; Triterpenes.
© 2014 ACG Publications. All rights reserved.
1. Plant Source
The Myrtaceae family is represented by 235 species in New Caledonia (NC), and 234 of them
are endemic to this island. Thus, all three species of Carpolepis are endemic to NC and has never been
investigated for their chemical content.
The leaves of Carpolepis laurifolia J.W.Dawson. were harvested in December 2009 at 480
meters high on the plateau de Tango (20°59'04'' S; 165°05'05' E ), in the North Province of NC
(harvesting authorization 609122852-2009). A voucher specimen (De Rus 27) was deposited at
Herbarium of the IRD center of Noumea (NOU) and identified by Dr. Jérome Munzinger (IRD).
Corresponding author: E- Mail:; Phone: 00687 290252.
Antoine et al., Rec. Nat. Prod. (2014) 8:3 286-289
2. Previous Studies
Since a few decades the dengue virus (DENV) became the most prevalent and widespread
arthropod borne virus affecting human and no treatment is available yet. In order to find new agents
for chemotherapy, the viral DENV-NS5 RNA polymerase (DENV-NS5 RdRp) has been identified as a
target of choice for antidengue drug research [1]. Previously, few natural compounds were described
for their inhibitory activity on the DENV-NS5 RdRp [2,3]. Among those compounds, biflavonoids
were the most active [4].
3. Present Study
During the screening of medicinal plants for antidengue activity, the crude extract obtained
from the leaves of Carpolepis laurifolia, an endemic species of Myrtaceae from NC, was found to be
particularly active on the DENV polymerase (91% inhibition at 10 µg/mL) and did not show any
cytotoxicity on MRC5 cells at 10 µg/mL. This plant was selected for further investigations. A
phytochemical screening led on the leaf powder underlined the abundance of flavonoids in leaves of
C. laurifolia which could be responsible of the antidengue potential of the plant.
340 g of dry leaf powder obtained from C. laurifolia were successively extracted at room
temperature with petroleum ether (3 × 1 L, 3h each) to obtain the fraction A (8.5 g) and with MeOH
80% (3 × 1 L, 3h each) to obtain fraction B (23.5 g). Methanolic extract (B) was reduced to 1 L and
extracted by EtOAc (3 × 1 L) to obtain B.2 (20 g). The petroleum ether extract (A) exhibited low
inhibitory activity on DENV-NS5 RdRp while methanol extract (B) and ethyle acetate part of
methanol extract (B.2) conserved the antidengue potential measured during the screening (data not
shown). The bioguided fractionation of B.2 allowed us to isolate five flavonoids (1-5) namely
quercetin (1), 6-methyl-7-methoxyapigenin (2), avicularin (3), quercitrin (4), hyperoside (5) together
with the triterpene betulinic acid (6). Purification was achieved by successive fractionations on silica
gel columns, Sephadex LH-20 and preparative HPLC. The purity of all tested compounds (> 95 %)
was assessed by HPLC-UV/MS. Spectroscopic data (MS,
H and
C NMR) of all compounds were
consistent with published data [5-7]. Copies of the original spectra are obtainable from the
corresponding author.
The biological activity on the DENV-NS5 RdRp of all compounds (Figure 1) was evaluated
individually and compared with four other commercial flavonoids: Isoquercitrine (7), spiraeoside (8),
quercetin-3,4’-di-O-glucoside (9) and rutin (10), purchased from Extrasynthèse. The DENV
polymerase activity was assayed by monitoring the incorporation of radiolabeled guanosine into a
homopolymeric cytosine RNA template, as previously described [8]. The d-GTP was used as positive
Among tested compounds, the active flavonoids (1, 3, 4, 8 and 10) exhibited IC
against the
DENV-NS5 RdRp ranging from 1.7 to 3.6 µM. The avicularine (3) was the most active flavonoid
tested here (IC
= 1.7 µM). According to the results obtained in this study (see Figure 1), the structure
of the genin significantly modulates the inhibitory activity of the DENV-NS5 RdRp and even small
modification of it can influence the activity measured on the DENV polymerase. Thus we can observe
that quercetin (1) was significantly more active than the C-methylapigenin derivative (2). Also, the
structure and position of the substituants on the quercetin modulated the inhibitory activity of the
DENV-NS5 RdRp. Indeed the avicularin (3) and quercitrin (4) with a rhamnose and arabinose
substituant in C3 respectively, demonstrated high inhibitory activity of DENV polymerase while the
activity dramatically decreased for hyperoside (5) and isoquercitrin (7) with a galactose and glucose in
the same position (Figure 1). Also, the spiraeoside (8) substituted by a glucose in C4’, strongly
inhibited the DENV-NS5 RdRp (IC
= 1.9 µM) whereas the additional glucose induced a loss of
activity for quercetin-3,4’-di-O-glucoside (9).
New inhibitors of the DENV-NS5 RdRp from Carpolepis laurifolia
1 (3.6 µM) 2 (> 30 µM) 3 (1.7 µM) 4 (2.1 µM)
5 (> 20 µM) 6 (1.7 µM) 7 (9.5 µM) 8 (1.9 µM)
9 (> 80 µM) 10 (2.1 µM)
Figure 1. Inhibition of the DENV-NS5 RdRp (IC
in µM) by compounds from C. laurifolia
(1-6) and other related commercial flavonoids monomers (7-10).
The flavonoids tested here have been previously described for various biological activities
including antiviral [9] but were tested for the first time for antidengue potential. We should note that
other flavonoids were previously described for antidengue activity [3, 10, 11]. Interestingly, betulinic
acid (6) isolated from C. laurifolia, was one of the stronger inhibitor of the DENV-NS5 RrRp among
tested compounds (IC
= 1.7 µM). This compound was previously described for several biological
activities including antiviral activity against HIV [12] but it is the first report for antidengue potential
of a triterpene. It will be interesting in the future to evaluate the activity of other triterpene derivatives
on the DENV-NS5 RdRp.
To the most of our knowledge, this study represents the first phytochemical study of a
Carpolepis species, an endemic genus in New-Caledonia, from the Myrtaceae family. This plant
appeared to be rich in quercetin derivatives (such as 1, 3, 4 and 5). This result is consistent with the
literature since those quercetin derivatives are frequently observed in the Myrtaceae species. The
presence of C-methyl apigenin derivatives (such as 2), that are less common in plant kingdom,
confirms that Carpolepis genus belong to the clade of Metrosideroideæ, in the phylogeny of
Myrtaceae. Indeed, those compounds have been isolated in the leaves of several species of this group,
including Metrosideros spp. [13]. The leaf crude extract of this plant strongly inhibited the DENV-
NS5 RdRp and was not cytotoxic. Five flavonoids (1-5) and betulinic acid (6) were isolated from the
active fractions of this plant. The activity of all isolated compounds was determined individually on
the DENV-NS5 RdRp and compared with the activity of other four commercial flavonoids (7-10).
This study allowed us to identify five flavonoids (1, 3, 4, 8 and 10) and a triterpene (6), with high
potential for antidengue drug development.
This work was supported by a grant from the fond Pacifique. Authors are grateful to Karine
Leblanc for preparative HPLC. We also thank Aleksandra Grudniewska for the corrections and
commentaries of this article. The authors do not declare any conflict of interest with the presented data
from this article.
Antoine et al., Rec. Nat. Prod. (2014) 8:3 286-289
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© 2014 ACG Publications
... The modifications are categorized into two groups: sugar modifications and nucleobase modifications. Sugar modifications include studying the impact of changing the stereogenic configuration at positions 2 and 3 of the ribosyl ring and converting it to arabinose and xylose, respectively (structures 2 and 3, Fig. 2) [11]. Substitution of the hydroxyl group at the ribosyl 5-position with an amino or substituted amino groups can also mimic the triphosphate's binding (structures 4-8, Fig. 2). ...
... At least 7 bonds (4 and 9) and up to 15 H-bonds (12) are reported for the adenosine derivatives. In addition, few hydrophobic contacts are also reported in Table 1 for some compounds [maximum of three contacts (11)]. The active site residues D760 and D761 (bold residues in Table 1) are common and form H-bonding with all of the adenosine derivatives. ...
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... The compound numbers 33, 34, and 36 bearing natural quercetin nucleus and compound 35 are triterpene betulinic acid obtained from Carpolepis laurifolia, belonging to Myrtaceae, which has shown potential anti-dengue activity for the inhibition of RdRp. Coulerie et al. extracted the leaf of this plant and identified these hits against DENV-NS5 RdRp [27]. ...
... The compound numbers 63, 71, and 85 exhibited interactions with ARG158, PHE224, ASP225, whereas compounds 70 and 87 had interaction with LYS141, ARG158, and ASP225. The compound numbers 5,8,18,26,27,39,59,60, and 84 with four common amino acid interactions and the compounds 22, 25, 30, 52, 61-63, 70-71 and 87 bearing three common amino acid interactions exhibited moderate binding affinity having docking score within the range of -6.3 to -7.79 Kcal/Mol. The compounds 33, 51, and 67 produced two common amino acid interactions in comparison to the reference compound that produced binding energies at a decreasing affinity order of -7.3833, -6.39792, and -5.01022 Kcal/Mol. ...
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... The activity of hyperoside (14) and isoquercitrin (15) dramatically decreased due to the presence of galactose and glucose in the same position. In contrast, spiraeoside (16) substituted by glucose in C4 showed strong inhibitory activity with an IC 50 1.9 µM and the addi-tional glucose-induced suppression of activity for quercetin-3,4'-di-O-glucoside (17) [83]. In conclusion, 7′′-O-methylamentoflavone (Sotetsuflavone, IC 50 0.16 µM) (7) was the most potent among all the flavonoids that have been tested for anti-DENV RdRp activity [84][85][86]. ...
... Betulin derivatives have been previously reported for their anti-viral activity against a range of viruses, including HIV, Sindbis virus, and Semliki Forest virus [37]. Another derivative, Betulinic acid 3β-caffeate (35), is a very potent inhibitor of DENV RdRp activity [83,84,93,95]. Fig. (6). ...
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... In natural product isolation work, Coulerie et al. isolated five flavonoids and betulinic acid from leaf extracts obtained from Carpolepis laurifolia [76]. These six isolated compounds and another four commercially available flavonoid derivatives were then tested for inhibition of DENV NS5 RdRp. ...
... These six isolated compounds and another four commercially available flavonoid derivatives were then tested for inhibition of DENV NS5 RdRp. Among them (Fig. 11), avicularin (35), quercitrin (36), betulinic acid (37), spiraeoside (38) and rutin (39) showed inhibition of DENV NS5 RdRp with IC 50 values ranging from 1.7 to 2.1 mM [76]. ...
... Hence, quercitrin represents a promising therapeutic agent for preventing diabetic complications, such as neuropathy, nephropathy, retinopathy, and cataracts [63,64]. In addition, quercitrin has been observed to interfere with dengue virus (DENV) replication with IC50 of 2.1 µM [65] Another promising flavonol is isorhamnetin (3). This molecule was isolated from leaves of Strychnos pseudoquina (Loganiaceae), a plant popularly known as "quina do campo" [66]. ...
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The book focuses on the molecular mechanisms underlying the pharmacological properties of flavonoids. Flavonoids are the phenolic compounds present in many fruits and vegetables, and they are most commonly consumed by humans through diet. All the different classes of flavonoids like the flavanones, flavones, anthocyanins and catechins have been observed to exhibit a variety of pharmacological actions. Though the flavonoids are known to interact with many of the cellular targets, only recently there has been a great interest among the scientist to delineate the molecular mechanism of action of flavonoids. Since understanding the molecular mechanism is very much important for predicting the clinical feasibility of a drug, this edited volume has been designed to collect and compile the information’s available on the molecular mechanisms of flavonoids as review article. The book comprises of 14 chapters and each chapter summarizes on the progress made in the flavonoid research, for the treatment of various disorders like cancer, diabetes, infectious diseases and so on. The available literatures on the molecular mechanism of the flavonoids are discussed in all the chapters, which will promote the researchers for further investigation on the pharmacological applications of flavonoids.
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Dengue virus is the world's most prevalent human pathogenic arbovirus. There is currently no treatment or vaccine, and solutions are urgently needed. We previously demonstrated that biflavonoids from Dacrydium balansae, an endemic gymnosperm from New Caledonia, are potent inhibitors of the Dengue virus NS5 RNA-dependent RNA polymerase. Herein we describe the structure-activity relationship study of 23 compounds: biflavonoids from D. balansae (1-4) and from D. araucarioides (5-10), hexamethyl-amentoflavone (11), cupressuflavone (12), and apigenin derivatives (13-23). We conclude that 1) over the four different biflavonoid skeletons tested, amentoflavone (1) and robustaflavone (5) are the most promising ones for antidengue drug development, 2) the number and position of methyl groups on the biflavonoid moiety modulate their inhibition of Dengue virus NS5 RNA-dependent RNA polymerase, and 3) the degree of oxygenation of flavonoid monomers influences their antidengue potential. Sotetsuflavone (8), with an IC50 = 0.16 µM, is the most active compound of this series and is the strongest inhibitor of the Dengue virus NS5 RNA-dependent RNA polymerase described in the literature.
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In order to find new molecules for antiviral drug design, we screened 102 ethyl acetate extracts from New-Caledonian flora for antiviral activity against the dengue 2 virus RNA-dependant RNA polymerase (DV-NS5 RdRp). The leaf extract of Dacrydium balansae, which strongly inhibited the DV-NS5, was submitted to bioguided fractionation. Four biflavonoids ( 1- 4), three sterols ( 5- 7), and two stilbene derivatives ( 8- 9) were identified and evaluated for their antiviral potential on the DV-NS5 RdRp. Biflavonoids appeared to be potent inhibitors of DV-NS5 RdRp with IC (50)s between 0.26 and 3.12 µM. Inhibitory activity evaluations against the RNA polymerase from other Flaviviridae viruses allowed us to conclude that these compounds are specific inhibitors of the DV RNA polymerase. The strongest inhibitions were observed with hinokiflavone ( 4), but podocarpusflavone A ( 2) is the strongest noncytotoxic inhibitor of the DV-NS5 and it also displayed polymerase inhibitory activity in a DV replicon. A preliminary structure-activity relationship study (SARs) revealed the necessity of the biflavonoid skeleton, the influence of number and position of methoxylations, and the importance of a free rotation of the linkage between the two apigenin monomers of the biflavonoids. To the best of our knowledge, podocarpusflavone A ( 2) is the strongest noncytotoxic non-nucleotide molecule exhibiting a specific inhibitory activity against the RNA polymerase domain of DV-NS5 and thus is promising for chemotherapy development against dengue fever.
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An in vitro screening of New Caledonian plants allowed the selection of several species with a significant dengue virus NS5 RNA-dependent RNA polymerase (RdRp) inhibiting activity. The chemical investigation of Cryptocarya chartacea led to the isolation of a series of new mono- and dialkylated flavanones named chartaceones A-F (1-6), along with pinocembrin. They were isolated as racemic mixtures and characterized using extensive one- and two-dimensional NMR spectroscopy. Four diastereomers of chartaceone A (1) were separated using chiral HPLC, and their absolute configurations were established by comparison of their experimental and calculated ECD spectra. The dialkylated flavanones, chartaceones C-F (3-6), exhibited the most significant NS5 RdRp inhibiting activity, with IC(50) ranging from 1.8 to 4.2 μM. Chartaceones represent a new class of non-nucleosidic inhibitors of the DENV NS5 RdRp.
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The thin waxy coatings on leaves of nine species of Callistemon, two of Melaleuca and one species of Metrosideros, have been studied for the occurrence of leaf surface flavonoids. The Callistemon species and Metrosideros robusta exhibit only C-methylated flavonoids, while O-methyl flavonoids were detected in Melaleuca huegelii. The new natural C-methyl flavonol, 5,7-dihydroxy-3,8,4'-trimethoxy-6-C-methylflavone, was isolated from Metrosideros robusta. The leaf wax of Callistemon coccineus contains the novel C-methylflavonoid, 5,4'-dihydroxy-8-C-methyl-7-methoxy flavanone.
Development of anti-dengue therapy represents an urgent un-met medical need. Towards antiviral therapy, recent advances in crystal structures of DENV enzymes have led to the possibility of structure-based rational design of inhibitors for anti-dengue therapy. These include (i) the structure of the 'active' form of the DENV protease in complex with a peptide substrate; (ii) the structure of DENV methyltransferase bound to an inhibitor that selectively suppresses viral methyltransferase, but not human methyltransferases; (iii) the structure of DENV RNA-dependent RNA polymerase in complex with a small-molecule compound. This review summarizes the structural biology of these three key enzymes (protease, methyltransferase, and polymerase) that are essential for DENV replication. The new structural information has provided new avenues for development of anti-dengue therapy.
The effect of several naturally occurring dietary flavonoids including quercetin, naringin, hesperetin, and catechin on the infectivity and replication of herpes simplex virus type 1 (HSV-I), polio-virus type 1, parainfluenza virus type 3 (Pf-3), and respiratory syncytial virus (RSV) was studied in vitro in cell culture monolayers employing the technique of viral plaque reduction. Quercetin caused a concentration-dependent reduction in the infectivity of each virus. In addition, it reduced intracellular replication of each virus when monolayers were infected and subsequently cultured in medium containing quercetin. Preincubation of tissue culture cell monolayers with quercetin did not affect the ability of the viruses to infect or replicate in the tissue culture monolayers. Hesperetin had no effect on infectivity but it reduced intracellular replication of each of the viruses. Catechin inhibited the infectivity but not the replication of RSV and HSV-1 and had negligible effects on the other viruses. Naringin had no effect on either the infectivity or the replication of any of the viruses studied. Thus, naturally occurring flavonoids possess a variable spectrum of antiviral activity against certain RNA (RSV, Pf-3, polio) and DNA (HSV-1) viruses acting to inhibit infectivity and/or replication.
The application of a computer-assisted structure elucidation expert system, CISOC-SES, leading to the unequivocal 1H, 13C and NOE resonance assignment of betulinic acid, a biol. active triterpenoid with complicated NMR resonances, is described. The procedure consists of peak picking that is independent of background information, systematic interpretation of connectivity information from 2D NMR into bond constraints and resonance assignment based on the proposed structure. De novo structure generation based solely on the mol. formula and spectral data is also described. This application demonstrates the potential of efficient and systematic structure elucidation of natural products with modern high-resoln. NMR spectroscopy combined with artificial intelligence. [on SciFinder (R)]
In the present study we analysed the possible antiviral effect on dengue viruses of different flavonoids extracted and identified at the Chemistry Institute, UNAM, from the Mexican plants Tephrosia madrensis, Tephrosia viridiflora and Tephrosia crassifolia. The flavonoids glabranine and 7-O-methyl-glabranine presented 70% inhibition on the dengue virus at a concentration of 25 microM, while methyl-hildgardtol A, hildgardtol A and elongatine had no effect on viral growth. Our results show that glabranine and 7-O-methyl-glabranine isolated from Tephrosia s.p. exert a dose-dependent inhibitory effect in vitro on the dengue virus.
3beta-Hydroxy-lup-20(29)-en-28-oic acid (betulinic acid) is a pentacyclic lupane-type triterpene that is widely distributed throughout the plant kingdom. A variety of biological activities have been ascribed to betulinic acid including anti-inflammatory and in vitro antimalarial effects. However, betulinic acid is most highly regarded for its anti-HIV-1 activity and specific cytotoxicity against a variety of tumor cell lines. Interest in developing even more potent anti-HIV agents based on betulinic acid has led to the discovery of a host of highly active derivatives exhibiting greater potencies and better therapeutic indices than some current clinical anti-HIV agents. While its mechanism of action has not been fully determined, it has been shown that some betulinic acid analogs disrupt viral fusion to the cell in a post-binding step through interaction with the viral glycoprotein gp41 whereas others disrupt assembly and budding of the HIV-1 virus. With regard to its anticancer properties, betulinic acid was previously reported to exhibit selective cytotoxicity against several melanoma-derived cell lines. However, more recent work has demonstrated that betulinic acid is cytotoxic against other non-melanoma (neuroectodermal and malignant brain tumor) human tumor varieties. Betulinic acid appears to function by means of inducing apoptosis in cells irrespective of their p53 status. Because of its selective cytotoxicity against tumor cells and favorable therapeutic index, even at doses up to 500 mg/kg body weight, betulinic acid is a very promising new chemotherapeutic agent for the treatment of HIV infection and cancer.