J Adv Pharm Technol Res. 2011 Jul-Sep; 2(3): 144–150.
`doi: 10.4103/2231-4040.85527
`
`PMCID: PMC3217711
`
`Evaluation of several microcrystalline celluloses obtained from agricultural by-
`products
`John Rojas, Alvin Lopez, Santiago Guisao, and Carlos Ortiz
`
`Department of Pharmacy, School of Pharmaceutical Chemistry, University of Antioquia, Medellín, Colombia
`Address for correspondence: Dr. John Rojas, Department of Pharmacy, School of Pharmaceutical Chemistry, University of Antioquia, cll 67 #
`53-108, of. 1-1157, Medellin, Colombia E-mail: jrojasca@gmail.com
`
`Copyright : © Journal of Advanced Pharmaceutical Technology & Research
`
`This is an open-access article distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported, which
`permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
`
`Abstract
`Microcrystalline cellulose (MCCI) has been widely used as an excipient for direct compression due to its
`good flowability, compressibility, and compactibility. In this study, MCCI was obtained from agricultural by-
`products, such as corn cob, sugar cane bagasse, rice husk, and cotton by pursuing acid hydrolysis,
`neutralization, clarification, and drying steps. Further, infrared spectroscopy (IR), X-ray diffraction (XRD),
`optical microscopy, degree of polymerization (DP), and powder and tableting properties were evaluated and
`compared to those of Avicel PH101, Avicel PH102, and Avicel PH200. Except for the commercial products,
`all materials showed a DP from 55 to 97. Particles of commercial products and corn cob had an irregular
`shape, whereas bagasse particles were elongated and thick. Rice and cotton particles exhibited a flake-like
`and fiber-like shape, respectively. MCCI as obtained from rice husk and cotton was the most densified
`material, while that produced from corn cob and bagasse was bulky, porous, and more compressible. All
`products had a moisture content of less than 10% and yields from 7.4% to 60.4%. MCCI as obtained from
`bagasse was the most porous and compressible material among all materials. This product also showed the
`best tableting properties along with Avicel products. Likewise, all MCCI products obtained from the above-
`mentioned sources showed a more rapid disintegration time than that of Avicel products. These materials can
`be used as a potential source of MCCI in the production of solid dosage forms.
`
`Keywords: Agricultural by-products, direct compression excipient, microcrystalline cellulose
`
`INTRODUCTION
`Cellulose is the most abundant polymer in nature formed by glucose units linked through a β-1,4 glycosidic
`linkage. The linear chains of this polymer are bound together forming microfibrils which structure the cell
`wall in most plants. Microcrystalline cellulose (MCCI) is produced by acid hydrolysis of wood pulp. During
`this process, the amorphous regions of the microfibrils are eliminated leaving the most crystalline parts intact.
`[1] The resulting product is washed and spray dried to get a powder of the desirable size, density, and
`moisture content.[2] MCCI is widely used as a pharmaceutical aid for direct compression, wet and dry
`granulation. It is also employed for the production of solid dosage forms due to its good compressibility,
`compactibility, and loading capacity of drugs.[3] Further, it renders tablets of good hardness without the need
`of using high compression forces[4] and these compacts usually show a low friability.[5]
`
`Now-a-days, the impact of agricultural by-products on the environment and other threatened ecosystems is
`an issue to be resolved. This problem is more frequent in developing countries where most of these residues
`
`Page 1 of 11
`
`Grunenthal GmbH Exhibit 2037
`Rosellini v. Grunenthal GmbH
`IPR2016-00471
`
`

`
`are either burned or dumped into rivers.[6] As a result, these by-products contribute to the greenhouse effect,
`soil erosion, and pollution of the atmosphere and water sources.[7] Since most of these residues are cellulose-
`based materials, they represent a potential source of inexpensive MCCI. Further, they are abundant and
`accessible, and the production process involved in the production of MCCI is simple and economical.
`Moreover, the availability of wood in the world is decreasing, along with a growing demand for wood pulp
`in developing countries of Asia, Africa, and Latin America. For this reason, the agricultural by-products,
`different from wood pulp sources, can be employed as an alternative source for MCCI.
`
`The aim of this study was to evaluate the powder and tableting properties of MCCI obtained from rice husk,
`corn cob, sugar cane bagasse, and cotton, and compare those properties with commercial MCCIs named as
`Avicel PH101, Avicel PH102, and Avicel PH200. The reported cellulose content of these residues depends
`on the seasonal conditions and the source employed, ranging from 20% to 60%.[8–10]
`
`MATERIALS AND METHODS
`
`Materials
`Sodium hydroxide (lot 58051305C), sodium metabisulfite (lot 09120342), and sodium hypochlorite (15%
`v/v, lot 093852) were obtained from Carlo Erba (Rodano, Italy) and Quimicos LM SA (Medellin,
`Columbia), respectively. Concentrated hydrochloric acid (37%, lot k40039517) and MCCI (Avicel PH101,
`lot 6N608C, Avicel PH102, lot C0909048, Avicel PH200, lot 70637) were purchased from Merck
`(Darmstadt, Germany) and FMC BioPolymer (Philadelphia, PA), respectively. The agricultural residues
`were obtained from local farmer markets.
`
`Preparation of Microcrystalline Cellulose Powders
`Raw materials were dried in a convection oven (model ED 115 UL; Binder-USA, USA) until a moisture
`content of less than 5% was reached. The dried material was milled in a cutting mill (model 3, Wiley mill;
`Arthur H. Thomas Co., Philadelphia, PA, USA) to reach a particle size of less than 1 mm. Approximately,
`400 g of the milled powder was placed on a 5 l round bottom flask and a 5% NaOH solution was added to
`eliminate the traces of lignin with heating at 74°C for 3 h. The powder-to-NaOH solution ratio was ~1:10.
`The dispersion was then cooled at room temperature and washed with distilled water until reaching a pH
`between 5 and 7. The resulting material was then treated with an excess of sodium hypochlorite (~700 ml)
`for 24 h at room temperature to eliminate low-molecular-weight carbohydrates such as pectins, proteins,
`hemicelluloses, and some mineral components. The resulting material was then washed and filtrated until
`reaching a pH between 5 and 7. The powder thus obtained was hydrolyzed with a 2 N HCl solution at 80°C
`for 1 h to remove the amorphous regions of cellulose followed by washing and filtration steps. A second
`NaClO treatment for 24 h was employed followed by washing and filtration steps. The resulting powder was
`dried on a convection oven (model ED 115 UL, Binder-USA) at 60°C for 12 h until reaching a moisture
`content less than 10%. The dry powder was then passed through an oscillating granulator (Riddhi Pharma
`Machinery, Gulabnagar, Gujarat, India) equipped with a 100 mesh screen.
`
`The above procedure was repeated for rice husk except that a second NaOH treatment was conducted after
`the acid hydrolysis step. Further, cotton was not treated with NaOH since it did not possess lignin. However,
`this material required a treatment with ~100 g of sodium metabisulfite at 70°C for 2 h, a washing, and a final
`NaClO treatment for 24 h at room temperature to completely bleach the product.
`
`Fourier Transform Infrared Spectroscopy Characterization
`Approximately, 1 mg of the sample was mixed with 100 mg of KBr (both previously dried at 110°C for 4 h
`before being used) on an agate mortar and pestle. Pellets of these mixtures were then made on a portable
`press at a dwell time of 5 min and at a force of 10,000 pounds. The infrared spectra were collected between
`650 and 4000/ cm on a Perkin Elmer IR Spectrometer (Spectrum BX, PerKin Elmer, CA, USA) equipped
`with the Ommic software (Nicolet Corp., Madison, WI, USA). The resolution, interval length, and number
`
`Page 2 of 11
`
`

`
`of scans employed were 16, 2, and 16/ cm, respectively.
`
`Powder X-ray Diffraction Characterization
`Powder X-ray diffractions were conducted over a 5-45° 2θ range using a Siemens diffractometer (model
`D5000; Siemens Energy and Automation, Inc., Madison, WI, USA), equipped with a monochromatic CuKα
`(α = 1.5460 Å, α = 1.54438 Å) X-ray radiation. The step width was 0.020° 2θ/min with a time constant of
`1
`0.5 s. The Difrac plus Eva software, version 2.0 (Siemens Energy and Automatization, Inc.) was used to
`identify the crystalline peaks.
`
`2®
`
`Powder Properties
`The optical microphotographs were taken on an optical microscope (BM-180, Boeco, Germany) coupled
`with a digital camera (S8000fd, Fujifilm Corp., Japan). The true density was determined on a helium
`picnometer (AccuPyc II 1340, Micromeritics, USA) with ~2 g of the sample. The bulk density was
`determined by the ratio of 100 g of the sample divided by the measured volume in a graduated cylinder. The
`tap density was measured from the final volume of the tapped sample determined on the AUTO-TAP
`analyzer (AT-2; Quantachrome Instruments, USA). The Carr index was obtained from the following
`equation:
`
`Porosity (ε) of the powder was determined from the following equation:
`
` correspond to the porosity, bulk density, and true density of the powder,
`, and ρ
`where ε, ρ
`true
`bulk
`respectively. The Hausner ratio was determined from the bulk and tap densities according to the following
`relationship:
`
`HR = ρ
`
`, (3)
`
`/ρ
`tap bulk
`where ρ
` and ρ
`
` are the tap and bulk densities, respectively.
`
`tap
`bulk
`The angle of repose was measured on 30 g of the sample and poured on a glass funnel (having the outer and
`inner diameters of 74.8 and 6.5 mm, respectively). The angle of repose was obtained from the arctan
`function of the quotient of the height with the radius of the cone formed after pouring the powder through the
`funnel.
`
`Particle Size and Particle Size Distribution
`Samples were fractionated on a ROTAP sieve shaker (RX29, WS Tyler Co., Mentor, OH, USA) using 400,
`300, 250, 180, 120, 105, and 75 μm stainless steel sieves (Fisher Scientific Co., Pittsburgh, PA, USA),
`stacked together in the order written. Approximately 25 g of the sample was shaken for 30 min followed by
`weighing the fraction of the powder retained in each sieve.
`
`The geometric mean diameter, d , and particle size distribution were determined from the log-normal
`g
`distribution plot constructed between the mean diameter and the cumulative percent frequency using the
`Minitab software (v.15; Minitab, Inc., State College, PA, USA).
`
`The moisture content was obtained by a gravimetric method on a convection oven (STM 80; Rigor
`Scientific, Inc., Chicago, IL, USA) employing ~5 g of the sample at 105°C for 3 h.
`
`The degree of polymerization (DP) was obtained by the intrinsic viscosity method [η] at 25 ± 0.5°C using a
`Canon-Fenske capillary viscometer (cell size no. 50), and cupriethylenediamine hydroxide (CUEN) was
`
`Page 3 of 11
`
`

`
`used as a solvent.[11] The DP was found by the following relationship:
`
`DP = 190*[η] (4)
`
`The compressibility of the powder was obtained from the Kawakita equation:[12]
`
`where N is the tap number, V the initial volume, V the volume after n taps, “a” is a constant related to the
`i
`n
`total volume reduction of the powder bed (compressibility index), and “b” is a constant related to the resistant
`forces (friction/cohesion) to compression.[13]
`
`Tableting Properties
`
`Preparation of compacts
`Compacts weighting ~500 mg were made on a hydraulic press (Compac 060804; Indemec Ltd., Itagüí,
`Columbia) coupled with a 13 mm concave punches and die set. The pressure range used was between 0 and
`270 MPa.
`
`Disintegration time
`The USP/NP method was employed.[14] Briefly, a Hanson disintegrator (39-133-115; Hanson Research
`Corporation, Northridge, CA, USA) was used and operated at 30 strokes/ min. The medium employed was
`distilled water maintained at 37 ± 2°C.
`
`Compact tensile strength
`It was determined on a Vankel hardness tester (UK 200; Vankel, Manasquan, NJ, USA). Each compact was
`placed between the platens and the crushing force was then measured. The radial tensile strength (TS) values
`were obtained according to the Pitt et al. equation:[15]
`
`where F is the breaking force (N) needed to break the compact into two halves, D is the diameter of the
`compact (mm), t is the compact total thickness (mm), and w is the central cylinder thickness.
`
`Compact friability test
`
`A Vankel Friabilator apparatus was employed (FAB-25; Logan Instruments Corp., NJ, USA) at 25 rpm. The
`friability test was performed according to the USP specifications.[15] Briefly, 13 compacts, each weighing
`about 500 mg and made at ~180 psi, were placed in the rotating drum and operated for 100 cycles.
`Compacts were then dedusted and reweighed. The friability percentage value was calculated according to
`the following equation:
`
`where W and W are the initial and final weight, respectively.
`i
`f
`
`RESULTS AND DISCUSSION
`
`Production and Characterization of MCCI
`As seen in Figure 1, MCCI samples showed the following characteristic vibration peaks of cellulose:
`
`Page 4 of 11
`
`

`
`3445/cm corresponding to intramolecular OH stretching, including hydrogen bonds; 2898/cm due to CH and
`CH stretching; 1650/cm corresponding to OH from absorbed water; 1430/cm due to CH symmetric
`2
`2
`bending; 1375/cm due to CH bending; 1330/cm due to OH in-plane bending; 1161/cm due to C-O-C
`asymmetric stretching (β-glucosidic linkage); 1061/cm due to C-O/C-C stretching; and 898/cm
`corresponding to the asymmetric (rocking) C-1 (β-glycosidic linkage) out-of-plane stretching vibrations.
`[16,17]
`
`The powder XRD of MCCI obtained from the different sources and the commercial Avicel products is
`shown in Figure 2. It is well known that cellulose I exhibits a parallel arrangement of the chains.[18] This
`arrangement gives the following characteristic diffraction peaks at 14.8, 16.3, and 22.4° 2θ, confirming the
`presence of the cellulose I lattice corresponding to the 1 ī 0, 110, and 200 reflections, respectively.[19] A
`shoulder at 20.4° 2θ has also been identified in some cellulose I excipients.[20]
`
`The morphology of different MCCI materials is shown in Figure 3. The commercial powders were formed
`by particles of an irregular shape. They did not exhibit a fibrous morphology since the spray drying process
`used in their manufacture allowed for the formation of particle aggregates. Likewise, particles obtained from
`corn cob showed aggregates of an irregular and smooth shape. Conversely, bagasse particles were elongated
`and thick, whereas, rice and cotton particles showed a flake-like and a thin and fibrous shape, respectively.
`
`Powder Properties
`Table 1 shows the powder properties of the materials evaluated. MCCI obtained from cotton rendered the
`highest yield (60.4%), whereas that obtained from sugar cane bagasse had the lowest yield (7.4%). It has
`been reported that bagasse and cotton have a cellulose content of ~70% and 95%, respectively.[21] The
`MCCI content is expected to be lower than that reported in the literature since during the hydrolysis and
`washing steps, the abundant amorphous regions are solubilized and eliminated. The DP was strongly
`dependant on the source employed. The DP of MCCI obtained from cob, bagasse, and cotton was ~95. This
`indicates that the hydrolysis process with 2 N HCl removed the amorphous regions of cellulose leaving only
`the crystalline chains of about 95 unit length. In contrast, MCCI as obtained from rice husk rendered the
`lowest DP, indicating a short average length of the chains. The commercial Avicel samples had the largest
`DP. It is well known that Avicel products have a large DP since they are obtained from soft- and hardwoods
`which have originally a larger chain length (>1000).[22]
`3
`The true density of the products was ~1.6 g/cm and was slightly lower for rice husk, probably due to the
`lower DP presented. The geometric mean diameter of MCCI obtained from corn cob, bagasse, and cotton
`ranged from 113 to 131 μm. In contrast, MCCI as obtained from rice husk had the largest geometric mean
`(~240 μm). The particle size of all these materials was mainly dependant on the final sieving of the powder
`through a 100 mesh screen. Conversely, the particle size of Avicel PH101, Avicel PH102, and Avicel PH200
`was close to 42, 93, and 188 μm, respectively.[22]
`
`MCCI as obtained from rice husk and cotton presented the largest bulk and tap densities (~0.63 and 0.83
`3
`g/cm , respectively). As a result, these two materials presented the fastest flow and lowest powder porosity
`3
`values (0.63 and 0.65 g/cm and 60% and 59.7%, respectively). The possible effect of moisture is expected
`to be negligible for MCCI materials since in all cases, the moisture content was below 10%.
`
`The compressibility index or volume reduction tendency is shown in Table 1. Results show that MCCI
`produced from bagasse and Avicel products were the most compressible materials. This indicates that these
`materials are desirable to be used as a fillers or diluents of large-dose active ingredients. In contrast, MCCI as
`obtained from rice husk had the lowest volume reduction making it appropriate to formulate only low-dose
`active ingredients. This is due to the large particle size, high degree of densification, and low porosity
`exhibited by this material.
`
`Tableting Properties
`
`Page 5 of 11
`
`

`
`The variation of compact tensile strength with compression pressure is shown in Figure 4. Independent of the
`compression pressure used, Avicel products and MCCI as obtained from bagasse formed compacts with the
`highest tensile strength. In contrast, MCCI as obtained from rice husk, cotton, and corn cobs rendered
`compacts of comparable tensile strength. Results indicate that the source of MCCI had a major effect on the
`resulting compact tensile strength. For example, Avicel products which are produced from softwood
`followed by spray drying always rendered the strongest compacts. It has been reported that different natural
`sources of cellulose might affect the mechanical properties of the isolated fibers.[1] A compact with a high
`tensile strength is desirable when a formulation of a solid dosage form with a poorly compressible drug is
`desirable.
`
`The disintegration times of the compacts are shown in Figure 5. Independent of the compression pressure
`used, in all cases, MCCI materials produced from the agricultural by-products sources rendered compacts
`with lower disintegration times than those shown by Avicel products. Since Avicel materials rendered the
`strongest compacts, it is not surprising that these products showed the slowest disintegrating compacts. A
`short disintegration time is desirable when a formulation of a fast disintegrating compact is needed.
`
`CONCLUSION
`MCCI can be obtained from rice husk, sugar cane bagasse, corn cob, and cotton having a potential use as a
`direct compression agent. MCCI as produced from rice husk and cotton were the densest and least porous
`materials having the fastest flow and lowest compressibility. In contrast, MCCI as obtained from bagasse was
`the least dense and the most porous material and it was as compressible as Avicel products rendering
`compacts of good strength. All MCCI materials formed compacts of faster disintegration times than those of
`Avicel products. Results indicated that these sources offer an inexpensive and a simple method to produce
`MCCI for use in the manufacture of solid dosage forms.
`
`ACKNOWLEDGMENTS
`The authors thank professors Jorge Arango, Gloria Valencia, Isabel Henao, and Oscar Florez for providing
`us with the equipments and access to the laboratories needed to carry out this project. The authors Also thank
`CODI and the pharmacy department for sponsoring this project.
`
`Footnotes
`Source of Support: Nil
`Conflict of Interest: Nil.
`
`REFERENCES
`1. El-Sakhawy M, Hassan ML. Physical and mechanical properties of microcrystalline cellulose prepared
`from agricultural residues. Carbohyd Polym. 2007;67:1–10.
`
`2. Bhimte NA, Tayade PT. Evaluation of microcrystalline cellulose prepared from sisal fibers as a tablet
`excipient: A technical note. AAPS PharmSciTech. 2007;8:E1–7.
`
`3. Foster AA, Ibrahim MM, El-Zawawy WK. Coupled acid and enzyme mediated production of
`microcrystalline cellulose from corn cob and cotton gin waste. Cellulose. 2007;14:247–56.
`
`4. Ohwoavworhua FO, Adelakun TA, Okhamafe AO. Processing pharmaceutical grade microcrystalline
`cellulose from groundnut husk: Extraction methods and characterization. Int J Green Pharm. 2009;3:97–104.
`
`5. Wang DS, Shang ZQ. Evaluation of microcrystalline cellulose prepared from kenaf fibers. J Ind Eng
`Chem. 2010;16:152–6.
`
`6. Ramírez JJ, Martínez JD, Petro SL. Basic design of a fluidized bed gasifier for rice husk on a pilot scale.
`Latin Am Appl Res. 2007;37:299–306.
`
`Page 6 of 11
`
`

`
`7. Chungsangunsit T, Gheewala SH, Patumsawad S. Emission assessment of rice husk combustion for
`power production. World Acad Sci Eng Technol. 2009;53:1070–5.
`
`8. Faria LF, Barboza JC, Serra AA, Castro DE. Preparation of bleached cellulose from sugar cane bagasse
`for chemical processing. Cell Chem Technol. 1998;32:441–55.
`
`9. Valverde A, Sarria B, Monteagudo JP. Análisis comparativo de las características fisicoquímicas de la
`cascarilla de arroz. Scientia et Technica. 2007;13:255–60.
`
`10. Uhumwangho MU, Okor RS. Effect of humidity on the disintegrant property of α-cellulose, Part II: A
`technical note. AAPS PharmSciTech. 2005;06:E31–4. [PMCID: PMC2750408] [PubMed: 16353960]
`
`11. Meyer V. West Conshhocken, PA: ASTM International; 2006. Annual book of ASTM STM. Paints
`related Coatings and Aromatics.
`
`12. Kawakita K, Ludde KH. Some considerations on powder compression equations. Powder Technol.
`1971;4:61–8.
`
`13. Patel S, Kaushal AM, Bansal AK. Effect of particle size and compression force on compaction behavior
`and derived mathematical parameters of compressibility. Pharm Res. 2007;24:111–24. [PubMed: 17063396]
`
`14. USP 32/NF 27: U.S. Pharmacopeia the Standard of Quality. New York, USA: United States
`Pharmacopeial Convention; 2009. Pharmacopoeial Convention and the National Formulary.
`
`15. Pitt KG, Newton JM, Richardson R, Stanley P. The material tensile strength of convex-faced aspirin
`tablets. J Pharm Pharmacol. 1989;41:289–92. [PubMed: 2569513]
`
`16. Carrillo F, Colom X, Suñol JJ, Saurina J. Structural FTIR analysis and thermal characterization of lyocel
`and viscose-type fibers. Eur Polym J. 2004;40:2229–34.
`
`17. Zhbankov RG. New York: Consultants Bureau; 1964. Infrared Spectra of Cellulose and its Derivatives.
`
`18. Krassig H. Amsterdam: Gordon and Breach; 1996. Cellulose, structure, accessibility and reactivity,
`science.
`
`19. Klemm D, Philipp B, Heinze T, Heinze U. 2nd ed. New York: John Wiley and Sons; 1998.
`Comprehensive cellulose chemistry: Functionalization of cellulose.
`
`20. Kothari SH, Kumar V, Banker GS. Compression, compaction, and disintegration properties of low
`crystallinity celluloses produced using different agitation rates during their regeneration from phosphoric acid
`solutions. Int J Pharm. 2002;232:69–80. [PubMed: 14727882]
`
`21. Ilindra A, Dhake JD. Microcrystalline cellulose from bagasse and rice straw. Indian J Chem Technol.
`2008;15:497–9.
`
`22. Jonat S, Hasenzahl S, Drechsler M, Alberts P, Wagner KG, Schmidt PC. Investigation of compacted
`hydrophilic and hydrophobic colloidal silicon dioxides as glidants for pharmaceutical excipients. Powder
`Technol. 2004;141:31–43.
`
`Figures and Tables
`
`Figure 1
`
`Page 7 of 11
`
`

`
`FTIR spectra of MCCI produced from different sources
`
`Figure 2
`
`XRD difractograms of MCCI produced by different sources
`
`Figure 3
`
`Page 8 of 11
`
`

`
`Page 9 of 11
`
`Page 9 of 11
`
`

`
`MCCI microphotographies obtained from (a) bagasse, (b) corn cob, (c) rice husk, (d) cotton, (e) Avicel PH101, (f) Avicel
`PH102, (g) Avicel PH200
`
`Table 1
`
`Powder properties of MCCI obtained from different sources
`
`Figure 4
`
`Tensile strength of compacts made of MCCI obtained from different sources
`
`Page 10 of 11
`
`

`
`Figure 5
`
`Disintegration time of compacts made of MCCI obtained from different sources
`
`Articles from Journal of Advanced Pharmaceutical Technology & Research are provided here courtesy of
`Medknow Publications
`
`Page 11 of 11