Renewable Resources from Wild Sunflowers (Helianthus spp., Asteraceae)1 GERALD J. SEILER,2 MERLE E. CARR,3 AND MARVIN O. BAGBy3 Twenty-eight taxa of Helianthus collected throughout the United States and grown in a field nursery were evaluated for yields ofoil, polyphenol hydrocarbon, protein, and ash in above-ground biomass. Hydrocarbons were examinedfor the presence ofrubber, gutta, and waxes. Rubber and gutta were analyzedfor weight­ average molecular weight (Nl}\~ and molecular weight distribution (lvnVD). He­ lianthus ciliaris had the highest oil yield (3.7%) and was analyzedfor yield offatty acids and unsaponifiable matter. Jllost taxa had low pol.vphenol yields «10%), with H. strumosus having the highest (13.9%). Helianthus salicifolius yielded the most hydrocarbon (1.6%) and H. ciliaris had the highest protein content (13.4%). Natural rubber was present in 13 species ofwildsunflowers. Helianthus maximiliani 3 had the lowest Ji71w (29.8 x 10 ), while H. laevigatus had the highest (73.3 x 103). The MvVD ofrubberfrom sunflowers were within the range o/thosefor commercial rubbers. The lower molecular weight rubbers may have potential as plasticizing additives in commercial processing ofsynthetic polyisoprenes and as hydrocarbon feedstock for a synthetic petroleum industry. Erneuerbare Mittel Von Wilden Sonnenblumen (Helianthus spp., Asteraceae). Achtllndzwanzig Taxa von Helianthus, die iiberall in den Vereinigten Staaten gesammelt wurden und in einer Feldgartnerei angebaut wurden, wurden nach Gehalt von 01, Polyphenol, Kohlenhydrat, Protein, und Asche in der oberirdischen Biomasse bewertet. Kohlenhydrate wurden auf das Vorhandensein von Gummi, Gutta, und Wachs gepriiji. Bei Gummi und Gutta ,vurde das molekulare Durch­ schnittsgewicht (Jll}\~ und die molekulare Gewichtsverteilung (AIWD) analysiert. Helianthus ciliaris hatte den hochsten Olgehalt (3.79b) und del' Gehalt von Fett­ sauren und unverseifien Stoffen war analysiert. Die meisten Taxa hatten niedrige Polyphenolgehalte «10%) und H. strumosus den hochsten (13.9%). Helianthus salicifolius liefene die meisten Kohlenhydrate (1.6%) und H. ciliaris das meiste Protein (13.4%). Natilrliches Gummi war bei 13 Arten von wilden Sonnenblumen vorhanden. Helianthus maximiliani hatte den niedrigsten Ji71w (29.8 x 103) wah­ rend H. laevigatus den hochsten hatte (73.3 x 103). Das lvlWD von Gummi von Sonnenblumen lag innerhalb der Grenzen fill' industriellen Gummi. Das niedrige molekulare Gewicht von Gummi mag ein Potential als plastifizierendes Zusatz­ mittel bei der technischen Verarbeitung von synthetischen Polyisoprenen und als Kohlenhydrat (Futtel) Fiillmasse habell. Within the past decade, increased attention has been given to the need for developing plant species as alternative sources offuels, chemicals, feeds, and other I Received 15 May 1989; accepted 3 February 1990. 2 V.S.D.A., Agricultural Research Service, Conservation and Production Laboratory, Bushland, TX 79012; Present address: V.S.D.A., Agricultural Research Service, Northern Crop Science Laboratory, P.O. Box 5677, Fargo, ND 58105. 3 Research Chemists, V.S.D.A., Agricultural Research Service, Northern Regional Research Center, Peoria, IL 61604. Economic Botany, 45(1), 1991, pp. 4-15 © 1991, by the New York Botanical Garden, Bronx, NY 10458 1991] SEILER ET AL.: WILD SUNFLOWERS important materials. Such developments could reduce our nation's dependency on foreign sources of many strategic and essential materials and could stimulate economic growth in the United States (Knowles and Lessman 1984). Physical, chemical, and botanical characteristics of about 1100 plant species have been investigated at the U.S.D.A. Northern Regional Research Center, Peo­ ria, Illinois, as potential new plant sources ofindustrial raw materials (Buchanan et al. 1978; Carr 1985; Carr et al. 1985, 1986a, 1986b, 1986c; Carr and Bagby 1987; Cull 1983). The genus Helianthus contains 49 species occurring in a wide range ofhabitats (Schilling and Heiser 1981). In recent years, there has been much interest in developing and utilizing plants able to tolerate arid and semiarid conditions, particularly for industrial nonfood uses (Davis et al. 1983). Many wild sunflower species inhabit semiarid areas and may be potentially useful in those areas ifthey could serve as sources ofindustrial raw materials. Limited information is available concerning the chemical composition ofwild sunflower species. Forty-eight acces­ sions representing 39 taxa were examined for yields of nonpolar extractables (hydrocarbons, rubber, etc.), polar extractables (resins, sugars, etc.), and crude protein (Adams and Seiler 1984). Several species of Helianthus have been eval­ uated for rubber content, which varied from 0.8% in H. tuberosus to 1.93% in H. radula and H. resinosus (Stipanovic et al. 1980, 1982). The objective of our research was to evaluate 28 taxa of Helianthus collected throughout the United States and grown in a common nursery. Plant materials were analyzed using solvent extractable fractions referred to as "oil," "polyphe­ nol," "hydrocarbon," and "protein." EXPERIMENTAL Twenty-nine accessions of wild sunflowers representing 28 taxa (5 annual and 23 perennial) were grown in a nursery at Bushland, Texas, in 1982 (Table 1). The plots were arranged in a completely randomized design, with each accession replicated three times. A commercial hybrid, '894', was grown for comparison. Voucher specimens of all taxa were prepared and filed at the U.S.D.A. Conser­ vation and Production Research Laboratory herbarium, Bushland, Texas. Table 1 presents some general information for the species of wild sunflowers analyzed (Rogers et al. 1982). Plant biomass samples were collected as mature above-ground plants and al­ lowed to air dry completely (l5-30°C). The entire sample (400-1000 g) was ground in a Wiley mill to pass through 1-mm diameter holes. Subsamples of milled material were analyzed for moisture (volatiles), ash, and apparent crude protein (6.25 x %Kjeldahl nitrogen). Each milled subsample was extracted in a Soxhlet apparatus with acetone for 48 h, after which acetone was evaporated using a stream of nitrogen. The air-dried extract was partitioned between hexane and water: ethanol (1 :7) to obtain fractions referred to as "oil" and "polyphenol," respectively. After evaporation of the solvents, these fractions were oven-dried (l05°C, 2 h) and weighed for yield. After the 48-h acetone extraction, the residue of each plant sample was extracted with hexane for 48 h to obtain a fraction referred to as "hydrocarbon." The hexane was evaporated with a stream of ni­ trogen and the hydrocarbon was oven-dried (l05°C, 2 h) and weighed for yield. 6 ECONOMIC BOTANY [VOL. 45 If yield of oil was at least 3.0% on a moisture-free plant sample weight basis, the oil was analyzed by thin layer chromatography (TLC) for classes of lipid constituents and, after saponification, for yields of unsaponifiable matter (UM) and free fatty acids (FA). Ifyield ofhydrocarbon was at least 0.4%, the hydrocarbon was analyzed by infrared spectroscopy (IR) to detect the presence ofrubber, gutta, and/or waxes. Rubber and gutta were analyzed for weight-average molecular weight (Mw) and molecular weight distribution (MWD) by gel permeation chro­ matography (GPC). Weight-average molecular weights were calculated by the method of Harmon using a Q factor of 60.4, which is the average ofthe ratios of molecular weight and polymer chain length reported for Hevea and guayule (Swan­ son et al. 1979). Details ofthe various analytical procedures have been described by Carr (1985). RESULTS AND DISCUSSION Yields of oil, polyphenol, hydrocarbon, and protein are shown in Table 2. Oil yield ranged from 1.0% in H. tuberosus to 3.7% in H. ciliaris (Table 2). These yields were moderate compared to plant species previously analyzed where only 30 species had yields ofat least 6% oil, with a maximum of 11 % oil in Euphorbia dentata Michx. (Carr and Bagby 1987). Polyphenol yields were also moderate, varying from 2.9% in H. pumilus to 13.9% in H. strumosus (Table 2). A polyphenol yield of 20% is considered high (Carr and Bagby 1987). All but one species ofwild sunflower (H. strumosus) had less than a 10% polyphenol yield. Of 1100 species previously examined, about 100 had polyphenol yields of 15%, and only 1% had yields of 20% or more (Carr et al. 1985). Species yielding substantial amounts ofboth oil and polypheno1 are atypical and are generally trees or shrubs, particularly evergreens (Carr et al. 1986c). Yields of hydrocarbon were at least 0.6% in 12 of the sunflower species. The lowest yields <0.1% were found in H. argophyllus, H. debilis ssp. silvestris, H. petiolaris ssp. petiolaris, and H. pumilus. The first three species are annual, and the last is perennial. The highest yield ofhydrocarbon was found in H. salicifolius (1.6%), a perennial (Table 2). With few exceptions, yields of hydrocarbon have been low «2%) for over 1000 species collected from various regions ofthe United States (Carr 1985; Roth et al. 1982). Protein content of wild sunflower plant samples varied from 3.8% in H. tu­ berosus to 13.4% in H. ciliaris (Table 2). Cultivated sunflower, H. annuus, had a higher protein content (20.4%) than the wild sunflowers. In general, plant protein contents were lower than those previously reported for wild sunflowers (Adams and Seiler 1984; Seiler 1986). The difference in protein levels could be due to the different sampling times, different plant parts, and nitrogen fertility. The perennial species H. ciliaris, the only species to have an oil content greater than 3%, was analyzed further by TLC (Table 2). The lipid fraction contained a trace ofhydrocarbon, 25% unsaponifiable lipids (UM), and 53% fatty acids (FA). Extracted oils ofmost aboveground plant samples analyzed previously have con­ tained about 40-60% UM (Carr et al. 1985). The combined UM + FA yield for H. ciliaris was 78%, which is on the lower end of the range when compared to most plant oils previously analyzed where combined amounts of UM and FA TABLE 1. GENERAL INFORMATION FOR SPECIES OF SUNFLOWER ANALYZED. a '<) '<) .:: Primary Herbarium Annual geographic Species voucher Life Height, General precip.