Screening of Promising Chemotherapeutic Candidates from Plants against Human Adult T-Cell Leukemia/Lymphoma (VII): Active Principles from Thuja occidentalis L.

During the screening of novel chemotherapeutic candidates from plants against adult T-cell leukemia/lymphoma, we identified that the extracts of Thuja occidentalis (Cupressaceae) showed potent anti-proliferative activity in MT-1 and MT-2 cells. Therefore, we attempted to isolate the active components from this plant. We isolated and identified 32 compounds (1-32; eight lignans, 18 terpenoids, and six flavonoids) from the extracts of the leaves and cones. Their structures were determined by spectroscopic analysis. Several of the isolated compounds inhibited the growth of both cell lines. Lignans showed more potent activity than other classes of compounds. A comparison of the activities of compounds 1-8 revealed that the presence of a trans-lactone (linkage of C-6 to C-7) correlated with increased activity. Diterpenes showed moderate activity, and the presence of a ketone moiety at the C-7 position correlated with increased activity in compounds 12-21. In addition, biflavones showed moderate activity, and the presence of methoxy functions appeared to influence the activity of these compounds. Several lignans were lead compound of anti-cancer reagent (etoposide). In conclusion, not only lignans, but also diterpenes and/or biflavones, may be promising candidates for the treatment of adult T-cell leukemia/lymphoma.

Screening of Promising Chemotherapeutic Candidates from Plants against Human Adult T-Cell Leukemia/Lymphoma (VI): Cardenolides from Asclepias curassavica.

In the course of our screening program for novel chemotherapeutic candidates from plants against adult T-cell leukemia/lymphoma, the extracts of Asclepias curassavica L. showed potent activity against MT-1 and MT-2 cells. Therefore, we attempted to isolate their active components. We identified a new cardenolide, 19-dihydrocalactinic acid methyl ester (1), along with 16 known cardenolides (2-17). Their structures were determined on the basis of spectroscopic data. Almost all of the isolated cardenolides inhibited the growth of both tumor cell lines. All the doubly linked cardenolides (11-17) except for 14 showed more potent activity than the other cardenolides. A comparison of the activities of 11, 14 and 16 revealed that the presence of hydroxy or acetoxy functional groups at C-16 led to a decrease in the activity. The 50% effective concentration (EC50) value of calotropin (11) against MT-2 cells was comparable to the potency of the clinical antineoplastic drug doxorubicin. The cytotoxic effect of 11 toward normal mononuclear cells obtained from the peripheral blood (PB-MNCs) was observed at a concentration 6 to 12 times higher than that used to induce growth inhibition against MT-1 and MT-2 cells. The proportions of annexin V-positive cells after 72 h of treatment with 11 were increased, indicating that it significantly induced apoptosis in MT-1 and MT-2 cells in a concentration-dependent manner. Cell cycle experiments demonstrated that 11 arrested MT-1 and MT-2 cells at the G2/M phase. Therefore, compound 11 may be a promising candidate for the treatment of adult T-cell leukemia/lymphoma.

Two New Triterpene Glycosides in the Roots of Uraria crinita.

Two new triterpene glycosides, 24-deoxyoxytrogenin 3-O-α-L-rhamnopyranosyl (1→2)[ß-D-glucopyranosyl]-ß-D-galactopyranosyl (1→2)-ß-D-glucuronopyranoside and sophoradiol 3-O-α-L-rhamnopyranosyl (1→2)-ß-D-glucuronopyranosyl (1→2)-ß-D-glucuronopyranoside with four known glycosides were isolated from a Chinese natural medicine, the roots of Uraria crinita (L.) DESV. Their structures were determined by chemical and spectral methods.

Identification and characterization of organic and glycosidic acids in the crude resin glycoside fraction of Ipomoea alba seeds.

Resin glycosides act as laxatives in crude drugs derived from plants of the Convolvulaceae family. These compounds have exhibited antibacterial, ionophoric, anti-inflammatory, antiviral, and multidrug resistance-modulating properties, as well as cytotoxicity against cancer cells. This study investigated the organic acid, hydroxyl fatty acid, monosaccharide, and glycosidic acid components of the crude resin glycoside fraction obtained from the methanol extract of Ipomoea alba L. (Convolvulaceae) seeds, which was subjected to alkaline and acidic hydrolysis. The alkaline hydrolysis yielded acetic, isobutyric, (E)-2-methylbut-2-enoic, and 2S-methyl-3S-hydroxybutyric acids as organic acid components, along with a glycosidic acid fraction. The acidic hydrolysis of the glycosidic acid fraction resulted in the isolation of 11S-hydroxytetradecanoic and 11S-hydroxyhexadecanoic acids as hydroxyl fatty acid components, as well as d-glucose, d-quinovose, d-fucose, d-xylose, and l-rhamnose as monosaccharide components. In addition, 10 new glycosidic acid methyl esters were isolated from the glycosidic acid fraction treated with trimethylsilyldiazomethane-hexane, along with one known glycosidic acid methyl ester. Of these, eight compounds contained new glycans. Four of these compounds were unusual natural glycosides with four glycosidic linkages to one monosaccharide. Their structures were determined using MS and NMR spectral analyses, which provided valuable insights into the unique glycosidic composition of I. alba seeds.

Eleven new glycosidic acid methyl esters from the crude resin glycoside fraction of Ipomoea alba seeds.

Resin glycosides are characteristic of plants of the Convolvulaceae family and are well-known purgative ingredients in crude drugs, such as Rhizoma Jalapae, Orizaba Jalapa Tuber, and Pharbitidis Semen, which are used in traditional medicine and derived from plants belonging to this family. Isolated resin glycosides have demonstrated diverse biological activities, including antibacterial, ionophoric, anti-inflammatory, antiviral, and multidrug-resistance-modulating properties, as well as cytotoxicity against cancer cells. These compounds consist of hydroxyl fatty acid oligoglycosides (glycosidic acids), with portions of the saccharide moieties acylated with some organic acids to form the core structure. This study investigated the glycosidic acid components of a crude resin glycoside fraction obtained from a methanolic extract of Ipomoea alba L. seeds (Convolvulaceae). Eleven new glycosidic acid methyl esters and one known methyl ester were isolated from a glycosidic acid fraction treated with trimethylsilyldiazomethane in hexane. Their structures were determined using acidic hydrolysis and electrospray ionization-time of fight mass spectrometry and NMR spectral analyses. These compounds are penta-, tetra-, or triglycosides, with methyl 11S-hydroxytetradecanoate or methyl 11S-hydroxyhexadecanoate as the aglycone. Although D-quinovose and L-rhamnose are common monosaccharide components, the remaining monosaccharides are D-glucose, D-xylose, or D-fucose. The crude resin glycoside fraction showed non-negligible cytotoxicity against HL-60 human promyelocytic leukemia cells.

Four new resin glycosides from Ipomoea muricata seeds: muricatins XIV-XVII.

Ipomoea muricata (L.) Jacq. seeds (Convolvulaceae) are used as a traditional laxative and carminative medicine. Muricatins XIV (1), XV (2), XVI (3), and XVII (4), were isolated from I. muricata seeds as four new resin glycosides, along with seven known compounds, three of which were isolated for the first time as natural products; their structures were determined using MS and NMR spectroscopy. Compounds 1-4 are macrolactones (jalapins); the sugar moieties of 1, 2, and 4 are partially acylated with 2S-methylbutyric acid, while that of 3 is esterified with 2S-methylbutyric and 2S-methyl-3S-hydroxybutyric acids. In addition, the antiviral activities of the seven compounds obtained in this study, together with five known compounds obtained in our previous study into resin glycosides from I. muricata seeds, were evaluated against herpes simplex virus type 1 (HSV-1); their cytotoxicities against HL-60 human promyelocytic leukemia cells were also investigated. All examined jalapins exhibited similar or slightly weaker anti-HSV-1 activities than acyclovir, the positive control; however, the glycosidic acid of 4 was inactive, while its methyl ester was weakly active. On the other hand, cytotoxicity testing against HL-60 cells showed similar results to those observed during anti-HSV-1 activity testing, with the exception that one jalapin was less active.

Screening of promising chemotherapeutic candidates from plants against human adult T-cell leukemia/lymphoma (VIII): six new withanolides from Physalis philadelphica.

Adult T-cell leukemia/lymphoma (ATL) is a malignancy of mature peripheral T-lymphocytes caused by human T-cell leukemia virus type I (HTLV-I). There are an estimated 5-20 million HTLV-1-infected individuals worldwide. Conventional chemotherapeutic regimens used against other malignant lymphomas have been administered to patients with ATL, but the therapeutic outcomes of acute and lymphoma-type ATL remain extremely poor. In the course of our screening program for novel chemotherapeutic candidate compounds from plants against two human T-cell leukemia virus I-infected T-cell lines (MT-1 and MT-2), we screened 16 extracts obtained from different parts of 7 Solanaceae plants. We identified that the extracts of Physalis pruinosa and P. philadelphica showed potent anti-proliferative activity in MT-1 and MT-2 cells. In our previous study, we have isolated withanolides from extract of aerial parts of P. pruinosa and examined their structure-activity relationships. In addition, we are also investigating further structure-activity relationships about other withanolides from Solanaceae plants (Withania somnifera, Withania coagulans, Physalis angulate, Nicandra physalodes, Petunia hybrida, and Solanum cilistum). In this study, we attempted to isolate their active compounds against MT-1 and MT-2 from extracts of P. philadelphica. We identified 13 withanolides, including six newly isolated compounds [24R, 25S-4ß, 16ß, 20R-trihydroxy-1-oxowitha-2-en-5ß, 6 ß -epoxy-22,26-olide (1), 4ß, 7ß,20R-trihydroxy-1-oxowitha-2-en-5ß, 6ß -epoxy-22,26-olide (2), 17ß,20 S-dihydroxywithanone (3), 2,3-dihydro-3ß-methoxy-23ß-hydroxywithaphysacarpin (4), 3-O-(4-rhamnosyl)glucosyl-physalolactone B (5), and 17R, 20R, 22S, 23S, 24R, 25R-4ß, 5α, 6ß, 20ß, 22α -tetrahydroxy-16ß, 23-diepoxy-1-oxowitha-2-en-26, 23-olide (6)], from the extract and examined the structure-activity relationships. The 50% effective concentration of withaphysacarpin (compound 7) [MT-1: 0.10 µM and MT-2: 0.04 µM] was comparable to that of etoposide [MT-1: 0.08 µM and MT-2: 0.07 µM]. Therefore, withanolides might be promising candidates for the treatment of ATL.

Four new resin glycosides, calyhedins VII-X, from the rhizomes of Calystegia hederacea.

Four new resin glycosides with macrolactone structures (jalapins), namely, calyhedins VII (1)-X (4), were isolated from the rhizomes of Calystegia hederacea Wall. (Convolvulaceae). The structures of 1-4 were determined based on spectroscopic data. They were classified into three ring types: a 27-membered ring (1), a 22-membered ring (2, 3), and a 23-membered ring (4). Their sugar moieties were partially acylated using five organic acids, including (E)-2-methylbut-2-enoic acid, 2S-methylbutyric acid, and 2 R-methyl-3R-hydroxybutyric acid. Compound 4 was the first genuine resin glycoside with calyhedic acid F as the glycosidic acid component. Additionally, the cytotoxic activities of 1, 2, and 4 towards HL-60 human promyelocytic leukaemia cells were evaluated. All compounds demonstrated almost the same activity as the positive control, cisplatin.

Identification and characterization of organic and glycosidic acids in the crude resin glycoside fraction from the leaves and stems of Calystegia japonica.

The alkaline hydrolysis of the crude resin glycoside fraction from the leaves and stems of the plant Calystegia japonica Choisy (Convolvulaceae) yielded organic acid and glycosidic acid fractions. The organic acid fraction was esterified with p-bromophenacyl bromide to obtain p-bromophenacyl 2R-methyl-3R-hydroxybutyrate (1) and p-bromophenacyl (E)-2-methylbut-2-enoate (2). By treating the glycosidic acid fraction with trimethylsilyldiazomethane-hexane, seven new methyl esters of glycosidic acids, namely calyjaponic acid A methyl ester (3) calyjaponic acid B methyl ester (5), calyjaponic acid C methyl ester (6), calyjaponic acid D methyl ester (7), calyjaponic acid E methyl ester (8), calyjaponic acid F methyl ester (9), and calyjaponic acid G methyl ester (10), were isolated along with one known ester (4). Their structures were characterized based on spectroscopic and chemical analyses. Compounds 3-8 had the same sugar moiety, α-L-rhamnopyranosyl-(1 → 2)-O-ß-D-glucopyranosyl-(1 → 2)-[O-α-L-rhamnopyranosyl-(1 → 6)]-O-ß-D-glucopyranose, and the aglycones of 3-8 were methyl 3S,11S-dihydroxyhexadecanoate, methyl 3S,12S-dihydroxyhexadecanoate, methyl 11S-hydroxyhexadecanoate, methyl 11S-hydroxypentadecanoate, methyl 3S,11S-dihydroxypentadecanoate, and methyl 3S,12S-dihydroxypentadecanoate, respectively. Compounds 9 and 10 were derivatives of 3 and 4, respectively, in which the C-6 of the second glucosyl residue was methylated. Compounds 6-8 contained methyl esters of unusual odd-carbon fatty acids as aglycones. The cytotoxicity of the crude resin glycoside fraction and 3 against HL-60 human promyelocytic leukemia cells was evaluated further; both were either weakly active or inactive compared to the positive control, cisplatin.

Two new glycosidic acids, calyhedic acids E and F, in crude resin glycoside fraction from Calystegia hederacea.

Two new glycosidic acids, calyhedic acids E (1a) and F (2a), were isolated from the glycosidic acid fraction afforded by alkaline hydrolysis of the crude resin glycoside fraction obtained from whole plants of Calystegia hederacea Wall. Compounds 1a and 2a were characterised as 11S-hydroxyhexadecanoic acid 11-O-ß-D-glucopyranosyl-(1→6)-O-ß-D-glucopyranosyl-(1→6)-O-ß-D-glucopyranosyl-(1→3)-[O-α-L-rhamnopyranosyl-(1→2)]-O-ß-D-glucopyranosyl-(1→2)-ß-D-quinovopyranoside and an isomer of 1a, in which the 11S-hydroxyhexadecanoyl residue of 1a was replaced by a 12S-hydroxyhexadecanoyl residue, respectively, on the basis of spectroscopic data.

Two new resin glycosides, muricatins XII and XIII, from the seeds of Ipomoea muricata.

Two new resin glycosides, muricatins XII (1) and XIII (2), were isolated from the crude resin glycoside fraction of the seeds of Ipomoea muricata (L.) Jacq. (Convolvulaceae), along with three known ones, muricatins V (3), VI (4), and IX (5). Compounds 1 and 2 contained new glycosidic acids, muricatic acids E (1a) and F (2a), respectively. The structures of these compounds were determined using data obtained from spectroscopy measurements and chemical evidence. The results suggested that 1 and 2 have macrolactone structures (jalapins). Furthermore, the cytotoxic activity of the crude resin glycoside fraction and 3-5 against HL-60 human promyelocytic leukaemia cells was evaluated. All tested samples demonstrated cytotoxic activities.

Calyhedins I-VI: Resin glycosides from the rhizomes of Calystegia hederacea.

Six previously undescribed resin glycosides, calyhedins I-VI, were isolated from the rhizomes of Calystegia hederacea Wall., which are the first genuine resin glycosides isolated from C. hederacea. The structures of calyhedins I-VI were determined based on spectroscopic data and chemical evidence. All the compounds have macrolactone structures (jalapins), and their sugar moieties were partially acylated by five organic acids. Calyhedins I, II-V, and VI have 27-, 28-, and 23-membered rings, respectively, and calyhedins IV-VI are the first jalapins with a sugar chain consisting of seven monosaccharides. Additionally, the cytotoxic activity of calyhedins II and III toward HL-60 human promyelocytic leukemia cells was evaluated. Both compounds demonstrated almost the same activity as the positive control, cisplatin.

Development of sensitivity-improved fluorescence-linked immunosorbent assay using a fluorescent single-domain antibody against the bioactive naphthoquinone, plumbagin.

A fluorescent single-domain antibody (fluobody), a fusion protein of a green fluorescent protein extracted from Aequorea coerulescens (AcGFP), a mutant that has been codon-optimized for mammalian expression, and a single-chain variable fragment antibody (scFv), against plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone; PL) was successfully constructed and expressed in Escherichia coli. The expressed fluobody was purified, refolded, and characterized to develop a speedy, simple, and sensitive fluorescence-linked immunosorbent assay (FLISA) for the determination of PL. In this study, two kinds of fluobody containing PL-scFv at the N-terminus of AcGFP (N fluobody) or the C-terminus of AcGFP (C fluobody) were constructed with flexible amino acid linker (Gly(4)Ser)(2) between PL-scFv and AcGFP for comparative purposes. Characterization of the fluobodies revealed that the C fluobody has better properties as a probe for FLISA than the N fluobody because the fluorescence intensity of C fluobody was 18-fold higher than that of N fluobody. Moreover, C fluobody exhibited a fourfold-higher binding affinity than the N fluobody. More interestingly, the limit of detection for PL measurement in FLISA (24 ng mL(-1)) was improved to eightfold higher than that in conventional ELISA (0.2 microg mL(-1)), indicating that a sensitive immunoassay could be developed by using fluobody instead of monoclonal antibody or scFv.

Enzyme-linked immunosorbent assay for total isoflavonoids in Pueraria candollei using anti-puerarin and anti-daidzin polyclonal antibodies.

Pueraria candollei (White Kwao Khuer) is a medicinal plant containing puerarin, daidzin, genistin, daidzein, and genistein as major isoflavonoids used for its rejuvenating and estrogenic effects. In order to analyze these compounds, a single enzyme-linked immunosorbent assay (ELISA) for total isoflavonoids was developed using anti-puerarin and anti-daidzin polyclonal antibodies (PAbs). The range for calibration of isoflavonoids by ELISA was 0.05-6.25 microg/mL. Total isoflavonoid concentrations in P. candollei samples determined by the newly developed assay system showed good agreement with those analyzed by HPLC. Based on validation analysis, this analytical method by ELISA is a precise, accurate, and sensitive method for the determination of total isoflavonoids in P. candollei.

Identification and characterization of organic and glycosidic acids in crude resin glycoside fraction from Calystegia hederacea.

Resin glycosides are well known as the purgative ingredients, which are characteristic of convolvulaceous plants. Calystegia hederacea Wall. is a perennial herbaceous vine that is widespread throughout India and East Asia. All parts of this plant are used for the treatment of menoxenia, gonorrhea, etc. Alkaline hydrolysis of the crude resin glycoside fraction of the whole plants of C. hederacea yielded four new glycosidic acids, calyhedic acids A, B, C, and D, along with two known glycosidic acids, calysolic acids A and C, and three known organic acids, 2S-methylbutyric, tiglic, and 2R,3R-nilic acids. Their structures were characterized on the basis of spectroscopic data and chemical evidence. Calyhedic acids A, B, and D were penta-, hexa-, and hepta-glycosides of 12S-hydroxyhexadecanoic acid, respectively, and cayhedic acid C was an isomer of calyhedic acid D, in which the 12S-hydroxyhexadecanoyl residue of calyhedic acid D was replaced by a 11S-hydroxyhexadecanoyl residue. Additionally, cytotoxic activity toward HL-60 human promyelocytic leukemia cells of the crude resin glycoside fraction, the glycosidic acid fraction, calyhedic acid A, and calysolic acid A from C. hederacea was evaluated. Furthermore, to clarify the structure-activity relationship of resin glycosides, the activities of six genuine resin glycosides with calysolic acid A or calysolic acid C as the glycosidic acid, which were isolated from C. soldanella, were examined. Among them, the crude resin glycoside fraction and five genuine resin glycosides with macrolactone structures demonstrated clear cytotoxic activities, while the glycosidic acid fraction, calyhedric acid A, calysolic acid A, and a genuine non-macrolactone-type resin glycoside were either inactive or exhibited weaker activity than the tested macrolactone-type resin glycosides.

Delta(9)-tetrahydrocannabinol enhances an increase of plasma corticosterone levels induced by forced swim-stress.

The present study was designed to determine the effect of delta(9)-tetrahydrocannabinol (THC) on susceptibility to stress. We reported that THC significantly prolonged the immobility time during the forced swim-stress. The selective cannabinoid CB(1) receptor antagonist O-2050 significantly reduced the enhancement of immobility by THC. We investigated the effect of THC on levels of stress hormone corticosterone under non-stress and forced swim-stress conditions. THC did not affect plasma corticosterone levels under non-stress conditions. However, THC, together with forced swim-stress, significantly increased plasma corticosterone levels. This effect was inhibited by O-2050. This evidence suggests that THC, under stressful conditions, enhances the susceptibility of the hypothalamus-pituitary-adrenal-axis to stress via the CB(1) receptor, thereby increasing the risk of depression.

Three new diterpenoids from the fruit of Vitex agnus-castus.

Three new labdane-type diterpenoids, viteagnusins F, G, and H, were isolated from the hexane extract of fruit (chasteberry) of Vitex agnus-castus L. (Verbenaceae) along with seven known compounds including four labdane-type diterpenoids, one norlabdane-type diterpenoid, one aromadendrane-type sesquiterpenoid, and one flavonoid. The chemical structures of the three new labdane-type diterpenoids were determined on the basis of spectroscopic data as well as chemical evidence.

Screening of promising chemotherapeutic candidates from plants against human adult T-cell leukemia/lymphoma (V): coumarins and alkaloids from Boenninghausenia japonica and Ruta graveolens.

During the course of our studies towards the identification of promising chemotherapeutic candidates from plants against two human T-cell lymphotropic virus type I-infected T-cell lines (MT-1 and MT-2), we screened 17 extracts from 9 rutaceous plants against MT-1 and MT-2 cells. The extracts from the aerial parts and roots of Boenninghausenia japonica, as well as the leaves and roots of Ruta graveolens showed potent antiproliferative effects. After activity-guided fractionation, we isolated 44 compounds from two rutaceous plants, including three new compounds (1-3), which were classified into 26 coumarin analogs (13 coumarins, 8 furanocoumarins, 4 dihydrofuranocoumarins and one dihydropyranocoumarin), 15 alkaloid analogs (7 quinolone alkaloids, 4 acridone alkaloids, 3 furanoquinoline alkaloids and one tetrahydroacridone alkaloid) and 3 flavonoid glycosides. Structure-activity relationship studies were also evaluated. The coumarin compounds (2, 3 and 7-9) bearing a 3-dimethylallyl moiety showed potent activity. Similarly, of all the furanocoumarins evaluated in the current study, compound 17 bearing a 3-dimethylallyl group also showed potent activity. A dihydrofuranocoumarin (27) bearing a 3-dimethylallyl moiety showed the most potent activity. Following 27, compound 28 showed potent activity. These results therefore suggested that the presence of a 3-dimethylallyl moiety was important to the antiproliferative activity of these coumarin analogs.

Role of vasopressin V1a receptor in ∆9-tetrahydrocannabinol-induced cataleptic immobilization in mice.

RATIONALE: Cannabis is a widely used illicit substance. ∆9-tetrahydrocannabinol (THC), the major psychoactive component of cannabis, is known to cause catalepsy in rodents. Recent studies have shown that vasopressin V1a and V1b receptors are widely distributed in the central nervous system and are capable of influencing a wide variety of brain functions such as social behavior, emotionality, and learning and memory. OBJECTIVES: The present study was designed to examine the possible involvement of V1a and V1b receptors in THC-induced catalepsy-like immobilization. METHODS: The induction of catalepsy following treatment with THC (10 mg/kg, i.p.) or haloperidol (1 mg/kg, i.p.) was evaluated in wild-type (WT), V1a receptor knockout (V1aRKO), and V1b receptor knockout (V1bRKO) mice. The effect of treatment with the selective 5-hydroxytryptamine1A receptor antagonist WAY100635 (0.1 mg/kg, i.p.) on THC-induced catalepsy was also evaluated in V1aRKO mice. Moreover, the effects of the V1a receptor antagonist VMAX-357 and the V1b receptor antagonist ORG-52186 on THC-induced catalepsy were evaluated in ddY mice. RESULTS: THC and haloperidol markedly caused catalepsy in V1bRKO mice as well as in WT mice. However, V1aRKO mice exhibited a reduction in catalepsy induced by THC but not by haloperidol. WAY100635 dramatically enhanced THC-induced catalepsy in V1aRKO mice. Although VMAX-357 (10 mg/kg, p.o.) but not ORG-52186 significantly attenuated THC-induced catalepsy, it had no significant effect on the enhancement of THC-induced catalepsy by WAY100635 in ddY mice. CONCLUSIONS: These findings suggest that V1a receptor regulates THC-induced catalepsy-like immobilization.

Screening of promising chemotherapeutic candidates from plants against human adult T-cell leukemia/lymphoma (IV): phenanthroindolizidine alkaloids from Tylophora tanakae leaves.

Adult T-cell leukemia/lymphoma (ATL) is a malignancy of mature peripheral T lymphocytes caused by human T-cell lymphotropic virus type 1 (HTLV-1). There are an estimated 5 million to 20 million HTLV-1-infected individuals worldwide; their lifetime risk of developing ATL is 3-5 %, and high HTLV-1 proviral loads have been shown to be an independent risk factor. Although conventional chemotherapeutic regimens used against other malignant lymphomas have been administered to ATL patients, the prognosis is often poor. In previous studies, we screened 459 extracts from 344 plants to isolate components exhibiting antiproliferative activity against HTLV-1-infected T-cell lines (MT-1 and MT-2). In our continuing search for potential anti-HTLV-1 natural products, 15 extracts of Asclepiadaceae plants were further tested against MT-1 and MT-2 cells. The MeOH extract of aerial parts of Tylophora tanakae showed antiproliferative activity. Activity-guided fractionation resulted in the isolation of 6 phenanthroindolizidine alkaloids (including a new compound), and we examined their antiproliferative activity against MT-1 and MT-2 cells. The EC50 value of some of the alkaloids was in the low nanomolar range, comparable to that of the clinically used antineoplastic drug doxorubicin. Structure-activity relationship analyses suggested that a 14ß-hydroxy moiety is essential for activity against HTLV-1-infected T cells. In contrast, the presence of a 2-methoxy moiety, a 7-methoxy moiety, or an N-oxide moiety appears to reduce the potency of the antiproliferative activity against HTLV-1-infected T cells.