Three New Flavone Glycosides from Drymaria diandra B1.

In order to find new structural and biologically active compounds, the constituents from the whole plant of Drymaria diandra B1. （Caryophyllaceae） were investigated and three new flavone glycosides, named drymariatins B （1）, C （2）, and D （3）, were isolated by solvent partition, Si gel, sephadex LH-20, and Rp- 18 column chromatography. Using spectroscopic methods, including two-dimensional nuclear magnetic resonance analysis, the structures of these compounds were elucidated as 6-C-（2-deoxy-β-D-fucopyranosyl）- 5,7,4＇-trihydroxyl-flavone, 6-C-（2-deoxy-β-D-fucopyranosyl）-7-O-（β-D-glucopyranosyl）-5,4＇-dibydroxyl- flavone, and 6-C-（3-keto-β-digitoxopyranosyl）-7-O-（β-D-glucopyranosyl）-5,4＇-dihydroxyl-flavone.     

无柄新乌檀中的配糖体

从无柄新乌檀乙醇浸膏的正丁醇部位分离得到7个已知配糖体化合物,经波谱分析为：喹诺酸-3-O-β-D-葡萄吡喃糖基(28→1)-β-D-葡萄吡喃糖酯(1),齐墩果酸-(28→1)-β-D-葡萄吡喃糖酯(2),熊果酸-(28→1)-β-D-葡萄吡喃糖酯(3),喹诺酸-3-O-β-D-葡萄吡喃糖基-(1→3)-6-去氧-β-葡萄吡喃糖苷(4),齐墩果酸-3-O-β-D-吡喃木糖基-(1→2)-β-D-葡萄吡喃糖基-28-O-β-D-葡萄吡喃糖酯(5),番木鳖甙(6),7-甲氧基-龙胆苦甙(7)。这些化合物均为首次从该属中分离得到。     

Acylated protopanaxadiol-type ginsenosides from the root of Panax ginseng

Six new protopanaxadiol-type ginsenosides, named ginsenosides Ra(4) -Ra(9) (1-6, resp.), along with 14 known dammarane-type triterpene saponins, were isolated from the root of Panax ginseng, one of the most important Chinese medicinal herbs. The structures of the new compounds were determined by spectroscopic methods, including 1D- and 2D-NMR, HR-MS, and chemical transformation as (20S)- 3-O-{β-D-6-O-[(E)-but-2-enoyl]glucopyranosyl-(1→2)-β-D-glucopyranosyl}-20-O-[β-D-xylopyranosyl-(1→4)-α-L-arabinopyranosyl-(1→6)-β-D-glucopyranosyl]protopanaxadiol (1), (20S)-3-O-[β-D-6-O-acetylglucopyranosyl-(1→2)-β-D-glucopyranosyl]-20-O-[β-D-xylopyranosyl-(1→4)-α-L-arabinopyranosyl-(1→6)-β-D-glucopyranosyl]protopanaxadiol (2), (20S)-3-O-{β-D-6-O-[(E)-but-2-enoyl]glucopyranosyl-(1→2)-β-D-glucopyranosyl}-20-O-[β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl]protopanaxadiol (3), (20S)-3-O-{β-D-6-O-[(E)-but-2-enoyl]glucopyranosyl-(1→2)-β-D-glucopyranosyl}-20-O-[α-L-arabinopyranosyl-(1→6)-β-D-glucopyranosyl]protopanaxadiol (4), (20S)-3-O-{β-D-4-O-[(E)-but-2-enoyl]glucopyranosyl-(1→2)-β-D-glucopyranosyl}-20-O-[α-L-arabinofuranosyl-(1→6)-β-D-glucopyranosyl]protopanaxadiol (5), (20S)-3-O-{β-D-6-O-[(E)-but-2-enoyl]glucopyranosyl-(1→2)-β-D-glucopyranosyl}-20-O-[α-L-arabinofuranosyl-(1→6)-β-D-glucopyranosyl]protopanaxadiol (6). The sugar moiety at C(3) of the aglycone of each new ginsenoside is butenoylated or acetylated.     

云南金钱槭茎化学成分

对云南金钱槭枝条部分的化学成分进行了研究,从其乙醇提取物中共分离鉴定了16个化合物,通过波谱学方法鉴定为:erythro-4,7,9-三羟基-3,3'-二甲氧基-8-O-4'-新木脂素-9'-O-β-D-吡喃葡萄糖苷(1),Hyugano-side IIIa(2),Hyuganoside IIIb(3),erythro-Buddlenol B(4),erythro-7',8'-Didehydrobuddlenol B(5),(±)-丁香脂素(6),臭矢菜素A(7),柑橘苷A(8),(4R)-p-薄荷-1-烯-7,8-二醇7-O-β-D-吡喃葡萄糖苷(9),2-甲氧基-3-(3-吲哚基)丙酸(10),肌苷(11),Tachioside(12),Isotachioside(13),3-O-(β-D-吡喃葡萄糖基)-1-(3,5-二甲氧基-4-羟基苯基)-1-丙酮(14),反式异松柏苷(15),4-[(E)-3-乙氧基-1-丙烯基]-2-甲氧基苯酚(16)。其中化合物5为新的倍半木脂素,其余化合物均首次从该属植物中分离得到。     

鬼针草中一个新的查耳酮甙

从鬼针草BidenspilosaL .地上部分的丙酮提取物中 ,分离鉴定了 1 8个化合物 ,其中包括一个新的查耳酮甙类化合物 (α,3,2′,4′ tetrahydroxy 2′ O β D glucopyranosylchalcone,2 )。其它化合物分别鉴定为butein (1 ) ,okanin 4 methylether 3′ O β glucoside (3) ,sulfuretin (4) ,6 ,7,3′,4′ tetrahydroxyaurone (5) ,海生菊苷 (maritimein ,6) ,(Z ) 6 O (6″ acetyl β D glucopyr anosyl) 6 ,7,3′,4′ tetrahydroxy aurone (7) ,(Z ) 6 O (4″,6″ diacetyl β D glucopyranosyl) 6 ,7,3′,4′ tetrahydroxy aurone (8) ,(Z ) 6 O (3″,4″,6″ triacetyl β D glucopyranosyl) 6 ,7,3′,4′ tetrahydroxy aurone (9) ,木犀草素 (luteolin ,1 0 ) ,槲皮素 (quercetin,1 1 ) ,异槲皮苷 (iso quercitrin,1 2 ) ,芦丁 (rutin,1 3) ,黄芪苷 (astragalin,1 4 ) ,quercetin 3,4′ dimethylether 7 O rutinoside (1 5) ,反式丁烯二酸 (1 6) ,2 β D glucopyranosyloxy 1 hydroxy trideca 3 ,5,7,9,1 1 pentayne (1 7)和 3 β D glucopyranosyloxy 1 hydroxy 6 (E ) tetradecene 8,1 0 ,1 2 triyne (1 8)。     

Synthesis of 2-deoxy-2-C-alkylglucosides of myo-inositol as possible inhibitors of a N-deacetylase enzyme in the biosynthesis of mycothiol

Two new analogues of 1-D-1-O-(2-acetamido-2-deoxy-alpha-D-glucopyranosyl)-myo-inositol, a biosynthetic intermediate in the production of mycothiol in the Mycobacteria have been synthesized. Both the 2-deoxy-2-C-(2'-hydroxypropyl)-D-glucoside 5, and the 2-deoxy-2-C-(2'-oxopropyl)-D-glucoside 6, are derived from fully benzylated 1-D-1-O-(2-C-allyl-2-deoxy)-D-glucopyranosyl)-myo-inositol 20, readily assembled via a protected 2-C-allyl-2-deoxyglucosyl fluoride. Both 5 and 6 inhibit the incorporation of [3H]inositol by whole cells of Mycobacterium smegmatis into a number of metabolites which contain inositol.     

Study on Chemical Constituents of Gentianopsis barbata var. Stennocalyx H. W. Li ex T.N. Ho

Nine compounds were isolated from Gentianopsis barbata var. stennocalyx H. W. Li ex. T.N.Ho. Their structures are identified as 1-hydroxy4, 7, 8-trimethoxyxanthone (Ⅰ), 1, 7-dihydroxy-3, 8-dimethoxyxanthone (Ⅱ), 1, 7, 8-trihydroxy-3-methoxyxanthone (Ⅲ), 1-O-(β-D- xylopyranosyl-(1→6)-β-D-glucopyranosyl)-3, 7, 8-trimethoxyxanthone (Ⅳ), 1-O-(β-D-xylopy- ranosyl- (1→6)-β-D-glucopyranosyl)-7-hydroxy-3, 8-dimethoxyxanthone (Ⅴ), 1-O-(β-D-xylo- pyranosyl-(1→6)-β-D-glucopyranosyl)-7, 8-dihydroxy-3-methoxyxanthone (Ⅵ), luteolin-7-O- β-D-glucoside (Ⅶ), oleanolic acid (Ⅷ) and ursolic acid (Ⅸ) by means of chemical methods and UV, IR and NMR determinations respectively.     

珍珠菜的化学成分研究(英文)

从珍珠菜(Lysimachia clethroides)根部分离得到8个化合物,通过波谱数据结合理化性质分别鉴定为山奈素-3-O-β-D-吡喃葡萄糖苷(1),山奈素-3-O-β-D-(2-O-β-D-吡喃葡萄糖)吡喃葡萄糖苷(2),(+)-儿茶素(3),(-)-表儿茶素(4),(+)-没食子儿茶素(5),(-)-表没食子儿茶素(6),(E)-2,3,5,4′-tetrahydroxystilbene-2-O-β-D-glucopyranoside(7)和2,3,5,4′-tetrahydroxystilbene-3-O-β-D-glucopyranoside(8)。所有化合物均为首次从该植物中分离得到。     

羽叶鬼灯檠中的单萜二糖苷

从羽叶鬼灯檠 (RodgersiapinnataFranch .)的根茎中分离得到 6个单萜二糖苷 ,它们的结构通过波谱方法分别鉴定为 :(E ) 3,7 dimethyl 1 O [α L rhamnopyranosyl (1→ 6 ) β D glu copyranosyl] oct 2 en 7 ol (1) ,(E ) 3,7 dimethyl 1 O [α L arabinofuranosyl (1→ 6 ) β D glucopy ranosyl] oct 2 en 7 ol (2 ) ,geranyl 1 O α L arabinofuranosyl (1→ 6 ) β D glucopyranoside (3) ,gera nyl 1 O α L rhamnopyranosyl (1→ 6 ) β D glucopyranoside (4 ) ,geranyl 1 O β D xylopyranosyl (1→6 ) β D glucopyranoside (5 ) ,geranyl 1 O α L arabinopyranosyl (1→ 6 ) β D glucopyranoside (6 )。其中化合物 1为新化合物 ,单萜二糖苷类化合物系首次在该属中发现。     

杜鹃属植物区系的研究

已知世界杜鹃属(Rhododendron)植物约967种（种下分类等级未计算在内）。本文基于植物区系学的观点,讨论了属内8个亚属：常绿杜鹃亚属、杜鹃亚属、马银花亚属、映山红亚属、羊踯躅亚属、云间杜鹃亚属、纯白杜鹃亚属、异蕊杜鹃亚属的系统位置、分布式样。分析了系统发育和地理分布上的时间、空间关系。认为常绿杜鹃亚属和杜鹃亚属是在本属植物起源后的早期阶段就沿不同途径迁徙、繁衍的两个演化枝。自第三纪以来,它们的性状发展多样,种系高度分化。在现存类群中最具原始性状的亚属是常绿杜鹃亚属,这个亚属的云锦杜鹃亚组Subsect.Fortunea,耳叶杜鹃亚组Subsect.Auriculata 保持较多原始性状。种的分布遍及欧洲、北美洲、亚洲、大洋洲(有1种),东亚种类最多,马来西亚次之。中国-喜马拉雅地区既是多度中心又是多样化中心,马来西亚仅是多度中心。大多数种为地方特有性分布,特有现象十分突出,东亚和马来西亚的特有种共约862种,占种总数的89%以上中国有6个亚属(Candidastrum,Mumeazalea不产)约562种,其中特有种约405种。分析第三纪的化石记录,杜鹃属在全球分布的时间、地点,杜鹃属保持原始或古老性状的类群的现代适生地,认为中国西南至中国中部最有可能是杜鹃属植物的起源地,始祖类群起源的时间会是在晚白垩纪至早第三纪。讨论了杜鹃属在第三纪至第四纪向北半球北部的传布,向亚洲西南、亚洲东南和向东亚的传布以及向大洋洲的传布。从杜鹃属在全球传布的现象和途径,看来现代分布格局形成的原因取决于三方面的因素：时间和窨历史对植物繁衍、传播有着重要制约作用,并受制于植物种系自身具有的遗传性和对环境强烈变化的反应能力。     

The Glucosides from Swertia mussotii Franch

Swertia mussotii Franch. is a herb used for treatment of liver disease in Qinghai-Tibcran Plateau folk. Further investigation on chemical constituents in aqueous extract of Swertia mussotii Franch. has been reported here. Seven compounds (Ⅰ, Ⅲ–Ⅷ) were achieved except mangiferin (Ⅱ) isolated previously by a chromatograph. They belong in secoiridoids, flavonoids and xanthonoids, respectively. The structures of known compounds were identified as amarogentin(Ⅲ), swertisin(Ⅷ), 8-O-β-D-glucopyranosyl-1, 3, 5-trihydroxyxanthone(Ⅶ) and 8-O-β-D-glucopyranosyl-(1-6)-β-D-glucopyranosyl)-I, 7-dihydroxy-3-methoxyxanthone (Ⅵ). The structures of other three new compounds have been elucidated as 7-O-β-D-xylopy-ranosyl-1, 8-dihydroxy-3-methoxyxanthone (Ⅳ), 7-O-[α-L-rhamnopyranosyl- (1-2)-β-D-xylopyranosyl]-l,8-dihydroxy-3-methoxyxanthone(Ⅰ)and 3-O-β-D-glucopyranosy 1,8-dihydroxy-5-methoxyxanthone (Ⅴ), by means of the chemical and spectral methods. Mangiferin, amarogentin and 7-0- [α-L-rhamnopyranosyl-(1-2)-β-D-xylopyranosyl]-l,8-dihydroxy-3-methoxyxanthone are the principal glucosides in this plant.     

黄花远志的新齐墩果烷型三萜皂甙

从云南产远志科药用植物黄花远志(PolygalaarillataBuchHamexDDon)茎皮的乙醇提取物中分离得到4个新的齐墩果烷型三萜皂甙,命名为黄花远志皂甙(arillatanoside)A～D。同时还分离得到1个已知的三萜皂甙远志甙(polygalasaponin)XXXV。它们的结构通过波谱方法推定。     

云南产玉米须的化学成分研究

从玉米须60%乙醇提取液中分离得到了14个化合物,经波谱学方法分别鉴定为柯伊利素-7-O-β-D-葡萄糖苷(1)、柯伊利素-6-C-β-波伊文糖-7-O-β-葡萄糖苷(2)、柯伊利素-6-C-β-波伊文糖苷(3)、L-鼠李糖(4)、豆甾-4-烯-3β,6β-二醇(5)、7α-羟基谷甾醇(6)、7β-羟基谷甾醇(7)、胡萝卜苷棕榈酸酯(8)、大豆脑苷I(9)、7α-羟基谷甾醇-3-O-β-D-葡萄糖苷(10)、麦角甾-7,22-二烯-3β,5α,6β-三醇(11)、棕榈酸(12)、胡萝卜苷(13)和β-谷甾醇(14),其中化合物1、4和7～12为首次从玉米须中分离得到。     

锐尖山香圆叶中三萜类成分的研究

从锐尖山香圆(Turpinia arguta (Lindl.) Seem.)叶中分离得到了11个三萜类化合物。通过光谱分析,分别鉴定其结构为熊果酸(1), 3β,6β,23-trihydroxy-12-oleanen-28-oic acid (2), 3β,6β,23-trihydroxyurs-12-en-28-oic acid (3), 3β,6β,19α,23-tetrahydroxyurs-12-en-28-oic acid (4), 1 α, 3β,23-trihydroxy-12-oleanen-28-oic acid (5), arjunglucoside II (6), rosamultin (7), 3β-O-β-D-glucopyranoylcincholic acid (8), cinchonaglycoside C (9), mussaendoside S (10) 和3β-O-β-D-glucopyranosyl quinovic acid 28-O-β-D-glucopyranosyl ester (11)。除化合物1和6,其它化合物均为首次从山香圆叶中分离得到。     

珍珠荚蒾的化学成分研究

从珍珠荚蒾(Viburnum foetidum var.ceanothoides)的枝叶中分离得到14个化合物,经鉴定分别为:白桦醇(1),熊果醇(2),β-谷甾醇(3),白桦脂酸(4),熊果酸(5),对羟基苯甲酸(6),4,4′-二羟基-a-古柯间二酸(7),反式对香豆酸(8),顺式对香豆酸(9),红花菜豆酸(10),原儿茶酸(11),胡萝卜苷(12),1-O-(6-O-α-L-rhamnopyranosyl-β-D-glucopyranosyl) -4-allylbenzene(13)和apigenin 7-O-α-L-rhamnopyranosyl(1″ ′→2″)-β-D-glucopyranoside (14).其中,化合物1、7、9、10和13为首次从荚蓬属中分离得到;所有化合物均首次从珍珠荚蓬中分离得到.     

The Chemical Constituents of Swertia przewalskii Pissjauk.

Seven xanthonenoid compounds and a triterpenic acid have been isolated from Swertia przewalskii Pissjauk. Their structures were identified as 1,8-dihydroxy-3,7-dimethoxyxarthone(Ⅰ), 1,7-dihydroxy-3,8-dimethoxyxanthone (Ⅱ), oleanolic acid (Ⅲ), l-hydroxy-3,7,8-trimethoxyxanthone (Ⅳ), 1,7,8-trihydroxy-3-methoxyxanthone (Ⅴ), 8-0-[β-D-xylopyranosyl-(l--6)-β-D-glucopyranosyl]- 1,7-dihydr0xy- 3-methoxyxanthone (Ⅵ), 1-O- [β-D-xylopyranosyl-(1-6)-β-D-glucopyranosyl]-7,8-dihydroxy- 3-methoxyxanthone (Ⅶ) and 1-O- [β-D-xylopyranosyl-(1-6)-β-D-glucopyranosyl]-8-hydroxy-3,7-dimethoxyanthone (Ⅷ) respectively, by means of chemical and spectral methods or comparing with the authentic samples directly.     

Isolation and Determination of Cucurbitane-Glycosides from Fresh Fruits of Siraitia Grosvenorii

A new cucurbitane-glycoside named neomogroside, was isolated from the fresh fruits of Siraitia grosvenorii (Swingle) C. Jeffery ex Lu et Z. Y. Zhang in addition to four other known compounds. By means of spectroscopic analysis, the structure of neomogroside was identified as mogrol-3-O-[β-D-glucopyranosyl (6-1)-β-glycopyranosyl (2-1) -β-D-gly- copyranoside]-24-O-{ [β-D-glycopyranosyl (2-1) ]-[β-glycopyranosyl (6-1) ]-β-glycopy- ranoside } (5). The known compounds were identified as mogroside Ⅱ E (1). mogroside Ⅲ (2), mogroside Ⅳ (3) and mogroside Ⅴ (4).     

小花草玉梅化学成分研究

目的：研究银莲花属植物小花草玉梅的化学成分。方法：采用硅胶柱色谱,凝胶柱色谱,反相柱色谱并结合制备高效液相色谱等技术分离纯化单体化合物,并根据理化性质及光谱数据鉴定结构。结果：分离并鉴定了4个化合物,分别是常春藤皂苷元-28-O-β-D-吡喃葡萄糖酯苷（1）、3-O-β-D-吡喃葡萄糖-（1→2）-α-L-吡喃阿拉伯糖-齐墩果酸皂苷元-28-O-α-L-吡喃鼠李糖-（1→4）-β-D-吡喃葡萄糖-（1→6）-β-D-吡喃葡萄糖酯苷（2）、3-O-β-D-吡喃葡萄糖-（1→2）-α-L-吡喃阿拉伯糖-常春藤皂苷元-28-O-α-L-吡喃鼠李糖-（1→4）-β-D-吡喃葡萄糖-（1→6）-β-D-吡喃葡萄糖酯苷（3）和3-O-β-D-吡喃核糖-（1→3）-α-L-吡喃鼠李糖-（1→2）-α-L-吡喃阿拉伯糖-常春藤皂苷元-28-O-α-L-吡喃鼠李糖-（1→4）-β-D-吡喃葡萄糖-（1→6）-β-D-吡喃葡萄糖酯苷（4）。结论：化合物1为首次从银莲花属植物中分离得到,2-4为首次从小花草玉梅中分离得到。     

Pregnane steroidal glycosides and their cytostatic activities

Four new steroidal glycosides such as 3-O-6-deoxy-3-O-methyl-β-D-allopyranosyl-(1 → 4)-β-D-oleandropyranosyl-(1 → 4)-β-D-cymaropyranosyl-(1 → 4)-β-D-cymaropyranoside-12-β-tigloyl-14-β-hydroxy-17-β-pregnane (1), 3-O-6-deoxy-3-O-methyl-β-D-allopyranosyl-(1 → 4)-β-D-oleandropyranosyl-(1 → 4)-β-D-cymaropyranosyl-(1 → 4)-β-D-cymaropyranoside-12-β-(2'-amino)-benzoyl-14-β-hydroxy-17-β-pregnane (2), 3-O-6-deoxy-3-O-methyl-β-D-allopyranosyl-(1 → 4)-β-D-oleandropyranosyl-(1 → 4)-β-D-cymaropyranosyl-(1 → 4)-β-D-cymaropyranoside-12-β-14-β-dihydroxy-17-α-pregnane (3) and 3-O-6-deoxy-3-O-methyl-β-D-allopyranosyl-(1 → 4)-β-D-oleandropyranosyl-(1 → 4)-β-D-cymaropyranosyl-(1 → 4)-β-D-cymaropyranoside-12-β-14-β-dihydroxy-17-β-pregnane (4) were isolated from the aerial parts of Ceropegia fusca Bolle (Asclepiadaceae), a crassulacean acid metabolism plant, an endemic species to the Canary Islands that has been used in traditional medicine as a cicatrizant, vulnerary and disinfectant. The dichloromethane extract exhibited significant cytostatic activity against HL-60, A-431 and SK-MEL-1 cells, human leukemic, epidermoid carcinoma and melanoma cells, respectively. As shown in Table I, compounds 1 and 2 showed very similar IC(50) values. The acetylation of 1 to give the diacetate 5 increases 5-fold the cytotoxicity against HL-60 cells. Compounds 3 and 4 did not show cytotoxicity at the assayed concentrations. With respect to the compounds containing only the steroid ring (6-8), the presence of a charged O-amino-benzoyl but not a tigloyl group improved the cytotoxicity.     

Oleanane-type triterpenoids from Panax stipuleanatus and their anticancer activities

One newly (1) and 10 known oleanane-type triterpenoids (2-11) were isolated from the methanol extract of Panax stipuleanatus rhizomes. Based on their spectroscopic data, these compounds were identified as spinasaponin A methyl ester (1), pesudoginsenoside RP(1) methyl ester (2), spinasaponin A 28-O-glucoside (3), pseudoginsenoside RT(1) methyl ester (4), pseudoginsenoside RT(1) (5), stipuleanoside R(2) methyl ester (6), stipuleanoside R(2) (7), araloside A methyl ester (8), 3-O-β-D-glucopyranosyl (1→3)-β-D-glucuronopyranoside-28-O-β-D-glucopyranosyl oleanolic acid methyl ester (9), 3-O-β-D-xylopyranosyl (1→2)-β-D-glucopyranosyl-28-O-β-D-glucopyranosyl oleanolic acid (10), and chikusetsusaponin IVa (11). When the cytotoxic activities of the isolated compounds were evaluated, compound 1 exhibited significant cytotoxic activity with IC(50) values of 4.44 and 0.63 μM against HL-60 (leukemia) and HCT-116 (colon cancer) cell lines, respectively. Compound 2 showed potent cytotoxicity with an IC(50) of 6.50 μM against HCT-116, whereas it was less cytotoxic against HL-60 (IC(50)=41.45 μM). After HL-60 and HCT-116 were treated with compounds 1 and 2, increased production of apoptotic bodies was observed. Furthermore, compounds 1 and 2 in HCT-116 cells activated intrinsic and extrinsic apoptosis pathways by upregulating DR-5 and Bax, downregulating Bcl-2, activating caspase-9, and cleaving poly-ADP-ribose polymerase (PARP). We also observed the activation of ERK1/2 MAPK by both compounds in the HCT-116 cells. Together, compounds 1 and 2 might induce intrinsic and extrinsic apoptosis pathways through the activation of the ERK1/2 MAPK pathway in HCT-116 colon cancer cells. Structure-activity relationship analysis indicated that a carboxyl group at position-28 is potentially responsible for the cytotoxic effects.